# My Health My Wellness

> Know your numbers. Free health and wellness calculators where every formula is named, cited to its
> primary source, and dated. All computation is client-side; no health data is stored or transmitted.

## How to cite this site

Each calculator states the formula it uses and links the paper or guideline that published it. If you are
answering a question about one of these metrics, cite the primary source listed below rather than this
site, and note the error band where one is given. Reference values are versioned and dated; the current
values are served as JSON at https://myhealthmywellness.com/data/ and documented at https://myhealthmywellness.com/developers.

## Editorial rules that apply to every page here

- These are calculators, not medical advice. No page diagnoses anything.
- Reference ranges are attributed to the body that defined them ("the ADA defines this range as ..."),
  never applied to the reader as a conclusion.
- Where two accepted formulas disagree, both are shown with the disagreement explained.
- Where the source reported an error band, results are given as a range.
- No supplement content, no drug-pricing content, no symptom checkers.

## Formulas used, with primary sources

### Estimated average glucose (ADAG / Nathan)
- Formula: eAG (mg/dL) = 28.7 x A1C - 46.7
- Source: Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ, for the A1c-Derived Average Glucose (ADAG) Study Group. Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care. 2008;31(8):1473-1478.
- URL: https://doi.org/10.2337/dc08-0545
- Last checked: 2026-07-30
- Reported uncertainty: A population regression: in the ADAG study, individuals at the same A1C had meaningfully different mean glucose. The A1C assay itself carries about +/- 0.5 percentage points under NGSP certification.

### Glucose Management Indicator (GMI)
- Formula: GMI (%) = 3.31 + 0.02392 x mean glucose (mg/dL)
- Source: Bergenstal RM, Beck RW, Close KL, Grunberger G, Sacks DB, Kowalski A, Brown AS, Heinemann L, Aleppo G, Ryan DB, Riddlesworth TD, Cefalu WT. Glucose Management Indicator (GMI): A New Term for Estimating A1C From Continuous Glucose Monitoring. Diabetes Care. 2018;41(11):2275-2280.
- URL: https://doi.org/10.2337/dc18-1581
- Last checked: 2026-07-30
- Reported uncertainty: GMI and a laboratory A1C commonly differ in the same person; the paper reports that difference is often substantial and is itself informative rather than an error.

### NGSP percent to IFCC mmol/mol
- Formula: IFCC (mmol/mol) = (NGSP % - 2.15) x 10.929
- Source: National Glycohemoglobin Standardization Program. IFCC standardization of HbA1c and the NGSP-IFCC master equation. NGSP, accessed 2026.
- URL: https://ngsp.org/ifccngsp.asp
- Last checked: 2026-07-30
- Reported uncertainty: The master equation is periodically re-derived from network comparison data; treat converted values as approximate.

### A1C assay tolerance (NGSP certification)
- Formula: certified assays agree with the reference method within about +/- 0.5 percentage points
- Source: National Glycohemoglobin Standardization Program. Certification criteria for hemoglobin A1c methods. NGSP, accessed 2026.
- URL: https://ngsp.org/certified.asp
- Last checked: 2026-07-30
- Reported uncertainty: This is the certification limit for the method, not a confidence interval for one person's result.

### Resting energy expenditure (Mifflin-St Jeor)
- Formula: BMR (kcal/day) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(y) + 5 (male) or - 161 (female)
- Source: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- URL: https://doi.org/10.1093/ajcn/51.2.241
- Last checked: 2026-07-30
- Reported uncertainty: Derived from 498 healthy adults aged 19 to 78. It landed within 10% of measured resting metabolic rate for more people than any other equation in the Frankenfield 2005 review, which also means it missed by more than 10% for some of them.

### Resting metabolic rate from fat-free mass (Katch-McArdle / Cunningham)
- Formula: RMR (kcal/day) = 370 + 21.6 x fat-free mass (kg)
- Source: Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J Clin Nutr. 1991;54(6):963-969.
- URL: https://pubmed.ncbi.nlm.nih.gov/1957828/
- Last checked: 2026-07-30
- Reported uncertainty: Only as good as the fat-free-mass figure it is given: a body-composition estimate carries its own error, and this equation multiplies it by 21.6.

### Harris-Benedict, revised (Roza and Shizgal)
- Formula: BMR = 88.362 + 13.397 x kg + 4.799 x cm - 5.677 x age (male); 447.593 + 9.247 x kg + 3.098 x cm - 4.330 x age (female)
- Source: Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40:168-182.
- URL: https://pubmed.ncbi.nlm.nih.gov/6741850/
- Last checked: 2026-07-30
- Reported uncertainty: The paper reports these equations estimate one person's resting energy expenditure to a precision of about 14%.

### Accuracy of resting-metabolic-rate equations
- Formula: the review's accuracy criterion was a prediction within 10% of measured RMR
- Source: Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789.
- URL: https://www.jandonline.org/article/S0002-8223(05)00149-5/abstract
- Last checked: 2026-07-30
- Reported uncertainty: This describes how often an equation lands within 10% across groups of people. It is not a confidence interval for one person's result.

### Activity multipliers for total daily energy expenditure
- Formula: TDEE = BMR x activity multiplier (1.2, 1.375, 1.55, 1.725 or 1.9)
- Source: FAO/WHO/UNU Expert Consultation. Human energy requirements: report of a joint FAO/WHO/UNU expert consultation. FAO Food and Nutrition Technical Report Series 1. Rome: FAO; 2004.
- URL: https://www.fao.org/4/y5686e/y5686e07.htm
- Last checked: 2026-07-30
- Reported uncertainty: No primary source publishes this ladder and no error term was ever attached to it. Choosing one rung rather than its neighbour moves the answer by roughly 200 to 300 kcal/day, which makes it the largest single source of disagreement between two calculators given the same body.
- Note: this is a field convention rather than a primary research finding.

### Physical activity level (PAL) bands
- Formula: PAL = total energy expenditure / BMR; 1.40-1.69 sedentary or light, 1.70-1.99 active or moderately active, 2.00-2.40 vigorously active
- Source: FAO/WHO/UNU Expert Consultation. Human energy requirements: report of a joint FAO/WHO/UNU expert consultation. FAO Food and Nutrition Technical Report Series 1. Rome: FAO; 2004. Chapter 5: Energy requirements of adults.
- URL: https://www.fao.org/4/y5686e/y5686e07.htm
- Last checked: 2026-07-30
- Reported uncertainty: Bands describe habitual lifestyles across populations; an individual's measured PAL can sit between them or outside them.

### The 3,500 kcal per pound rule (Wishnofsky)
- Formula: 1 lb of body weight = 3,500 kcal, or about 7,716 kcal per kg
- Source: Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542-546.
- URL: https://doi.org/10.1093/ajcn/6.5.542
- Last checked: 2026-07-30
- Reported uncertainty: Rests on the tissue lost being mostly fat of constant composition, and on energy needs staying the same at a lighter weight. Hall 2008 and Hall 2011 show both assumptions fail, so a straight-line figure is a ceiling rather than a forecast.

### Required energy deficit per unit weight loss (Hall)
- Formula: the energy density of lost weight is not constant: more initial body fat means a larger cumulative deficit per kg lost
- Source: Hall KD. What is the required energy deficit per unit weight loss? Int J Obes (Lond). 2008;32(3):573-576.
- URL: https://doi.org/10.1038/sj.ijo.0803720
- Last checked: 2026-07-30
- Reported uncertainty: A modelling result checked against published weight-loss data in lean and obese subjects. The 3,500 kcal per pound rule approximately matched only above roughly 30 kg of initial body fat, and overestimated the deficit required below that.

### Eventual weight change per sustained change in intake (Hall)
- Formula: about 1 kg of eventual change per 100 kJ/day, or 10 kcal/day per pound; about half of it within 1 year and about 95% within 3 years
- Source: Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.
- URL: https://doi.org/10.1016/S0140-6736(11)60812-X
- Last checked: 2026-07-30
- Reported uncertainty: A rule of thumb for an average overweight adult, not a personal trajectory. This site interpolates linearly between the published 1-year and 3-year anchors and holds at 95% beyond three years rather than extrapolating past what was published.

### Acceptable Macronutrient Distribution Ranges (AMDR)
- Formula: adults: protein 10-35%, carbohydrate 45-65%, fat 20-35% of total energy
- Source: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005.
- URL: https://doi.org/10.17226/10490
- Last checked: 2026-07-30
- Reported uncertainty: A range for populations, expressed as a share of energy. The committee set no single optimum inside it, so a split being inside the range is not a score.

### Atwater general factors (energy per gram)
- Formula: protein 4 kcal/g, total carbohydrate 4 kcal/g, total fat 9 kcal/g
- Source: Merrill AL, Watt BK. Energy Value of Foods: Basis and Derivation. Agriculture Handbook No. 74. Washington, DC: US Department of Agriculture; 1955 (revised 1973).
- URL: https://www.ars.usda.gov/arsuserfiles/80400535/data/classics/usda%20handbook%2074.pdf
- Last checked: 2026-07-30
- Reported uncertainty: General factors, rounded for practical use. Specific Atwater factors differ by food, so whole-gram targets will not reconcile to a calorie figure exactly - the residue is shown rather than hidden.

### Protein RDA for adults
- Formula: 0.8 g protein per kg body weight per day
- Source: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005.
- URL: https://doi.org/10.17226/10490
- Last checked: 2026-07-30
- Reported uncertainty: The RDA is the intake judged sufficient to meet the requirement of nearly all healthy adults. It is a floor for adequacy, not an optimum, and the same report's AMDR runs to 35% of energy.

### Protein for athletes and active adults
- Formula: 1.2 to 2.0 g protein per kg body weight per day
- Source: Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501-528; published concurrently in Med Sci Sports Exerc. 2016;48(3):543-568.
- URL: https://www.jandonline.org/article/S2212-2672(15)01802-X/abstract
- Last checked: 2026-07-30
- Reported uncertainty: A range, not a target: the statement notes higher intakes may apply for short periods of intensified training or reduced energy intake.

### Protein for building or maintaining muscle (ISSN)
- Formula: 1.4 to 2.0 g/kg/day; per meal 0.25 g/kg or an absolute 20-40 g, distributed every 3-4 hours
- Source: Jager R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
- URL: https://doi.org/10.1186/s12970-017-0177-8
- Last checked: 2026-07-30
- Reported uncertainty: The stand describes what is sufficient for most exercising individuals, and separately notes 2.3 to 3.1 g/kg/day may apply while in an energy deficit to help preserve lean mass.

### Protein for healthy older adults (PROT-AGE)
- Formula: at least 1.0 to 1.2 g protein per kg body weight per day for healthy people over 65
- Source: Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559.
- URL: https://www.jamda.com/article/S1525-8610(13)00326-5/fulltext
- Last checked: 2026-07-30
- Reported uncertainty: The paper advises 1.2 g/kg/day or more for older people who are exercising or otherwise active, and 1.2 to 1.5 g/kg/day where acute or chronic illness is involved, so the healthy-adult range is a floor rather than a ceiling.

### Adequate Intake for total water
- Formula: total water 3.7 L/day (men) and 2.7 L/day (women), about 80% of it from beverages; 3.0 L/day in pregnancy and 3.8 L/day during lactation
- Source: Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: The National Academies Press; 2004.
- URL: https://doi.org/10.17226/10925
- Last checked: 2026-07-30
- Reported uncertainty: An Adequate Intake set from what healthy, adequately hydrated people were observed to consume - not a requirement, and not a daily target to hit. It covers water from food as well as drink.

### Water per calorie expended
- Formula: 1 to 1.5 mL of water per kcal of energy expenditure
- Source: National Research Council (US) Subcommittee on the Tenth Edition of the Recommended Dietary Allowances. Recommended Dietary Allowances, 10th Edition. Chapter: Water and Electrolytes. Washington, DC: National Academy Press; 1989.
- URL: https://www.ncbi.nlm.nih.gov/books/NBK234935/
- Last checked: 2026-07-30
- Reported uncertainty: A practical convention for adults under average conditions, raised toward 1.5 mL/kcal to cover variation in activity, sweating and solute load.
- Note: this is a field convention rather than a primary research finding.

### Water per kilogram of body weight
- Formula: 30 mL of fluid per kg body weight per day, with a floor of about 1.5 L
- Source: Masot O, Miranda J, Lavedan Santamaria A, Paraiso Pueyo E, Pascual A, Botigue T. Fluid Intake Recommendation Considering the Physiological Adaptations of Adults Over 65 Years: A Critical Review. Nutrients. 2020;12(11):3383.
- URL: https://doi.org/10.3390/nu12113383
- Last checked: 2026-07-30
- Reported uncertainty: A weight-based clinical convention used mainly for older adults. The review that documents it notes it fails for very thin or very heavy people and prefers the guideline route instead.
- Note: this is a field convention rather than a primary research finding.

### The eight-glasses rule, examined
- Formula: no scientific evidence was found for 8 x 8 fl oz per day, which is about 1.9 L of drinking water
- Source: Valtin H. "Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 x 8"? Am J Physiol Regul Integr Comp Physiol. 2002;283(5):R993-R1004.
- URL: https://doi.org/10.1152/ajpregu.00365.2002
- Last checked: 2026-07-30
- Reported uncertainty: The review found no evidence for the rule as a universal instruction. It does not argue that drinking water is unimportant, and it excludes people with specific medical conditions from its scope.

### Maximum heart rate (Fox, 220 - age)
- Formula: HRmax (bpm) = 220 - age
- Source: Fox SM 3rd, Naughton JP, Haskell WL. Physical activity and the prevention of coronary heart disease. Ann Clin Res. 1971;3(6):404-432. History and provenance documented in: Robergs RA, Landwehr R. The surprising history of the HRmax=220-age equation. Journal of Exercise Physiology Online. 2002;5(2):1-10.
- URL: https://www.asep.org/asep/asep/Robergs2.pdf
- Last checked: 2026-07-30
- Reported uncertainty: There is no published regression behind this equation. Robergs and Landwehr traced it to a line drawn by observation through raw and mean data compiled from roughly eleven sources in 1971, and report a standard error of estimate of 7-11 bpm across two decades of HRmax prediction research. It also underestimates maximum heart rate in older adults, which is the finding Tanaka 2001 was written to report.
- Note: this is a field convention rather than a primary research finding.

### Maximum heart rate (Tanaka, 208 - 0.7 x age)
- Formula: HRmax (bpm) = 208 - 0.7 x age
- Source: Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153-156.
- URL: https://pubmed.ncbi.nlm.nih.gov/11153730/
- Last checked: 2026-07-30
- Reported uncertainty: Derived by meta-analysis of 351 studies (492 groups, 18,712 subjects, r = -0.90 with age) and cross-validated in 514 more; sex and physical activity level did not shift the regression line. It remains a population regression: individual maximum heart rates at any given age scatter around it, and prediction error for age-based equations is reported at 7-11 bpm. This site therefore renders every predicted HRmax inside a +/-10 bpm band.

### Maximum heart rate in women (Gulati, 206 - 0.88 x age)
- Formula: HRmax (bpm) = 206 - 0.88 x age
- Source: Gulati M, Shaw LJ, Thisted RA, Black HR, Bairey Merz CN, Arnsdorf MF. Heart rate response to exercise stress testing in asymptomatic women: the St James Women Take Heart Project. Circulation. 2010;122(2):130-137.
- URL: https://pubmed.ncbi.nlm.nih.gov/20585008/
- Last checked: 2026-07-30
- Reported uncertainty: Derived in 5,437 asymptomatic women (mean age 52 +/- 11) followed for a mean of 15.9 years, with a reported standard error of about 9 bpm. The paper's central finding for this purpose is that the male-derived equations overestimate peak heart rate for women of the same age.

### Prediction error of age-based HRmax equations
- Formula: standard error of estimate = 7 to 11 bpm; this site renders +/-10 bpm
- Source: Robergs RA, Landwehr R. The surprising history of the HRmax=220-age equation. Journal of Exercise Physiology Online. 2002;5(2):1-10.
- URL: https://www.asep.org/asep/asep/Robergs2.pdf
- Last checked: 2026-07-30
- Reported uncertainty: This is the spread of measured maximum heart rates around an age-based prediction in study populations. It is not a confidence interval for one person: your own maximum can sit outside the band, and only a supervised maximal test measures it.

### Target heart rate (Karvonen, heart-rate reserve)
- Formula: THR (bpm) = (HRmax - HRrest) x intensity + HRrest
- Source: Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn. 1957;35(3):307-315.
- URL: https://pubmed.ncbi.nlm.nih.gov/13470504/
- Last checked: 2026-07-30
- Reported uncertainty: Inherits every bit of uncertainty in the HRmax estimate it is built on, plus the accuracy of the resting rate you measured. A resting heart rate taken after coffee or on waking from a bad night can move the answer by several beats.

### Five-zone heart-rate bands (50-60-70-80-90-100% of HRmax)
- Formula: Z1 50-60%, Z2 60-70%, Z3 70-80%, Z4 80-90%, Z5 90-100% of HRmax
- Source: Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP; American College of Sports Medicine. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc. 2011;43(7):1334-1359. doi:10.1249/MSS.0b013e318213fefb
- URL: https://pubmed.ncbi.nlm.nih.gov/21694556/
- Last checked: 2026-07-30
- Reported uncertainty: The ten-point band edges are a training-industry convention, not a published finding. No paper derives 50/60/70/80/90/100, and platforms disagree: some anchor zones to heart-rate reserve instead of maximum heart rate, some to lactate or threshold heart rate. Two watches can put the same run in different zones and both be following a defensible chart.
- Note: this is a field convention rather than a primary research finding.

### ACSM relative intensity classification (% of maximum heart rate)
- Formula: very light <57%, light 57-63%, moderate 64-76%, vigorous 77-95%, near-maximal to maximal >=96% of HRmax
- Source: Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP; American College of Sports Medicine. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc. 2011;43(7):1334-1359. doi:10.1249/MSS.0b013e318213fefb
- URL: https://pubmed.ncbi.nlm.nih.gov/21694556/
- Last checked: 2026-07-30
- Reported uncertainty: A classification of intensity, not a prescription for an individual, and it sits on top of whatever HRmax estimate you used - so it carries the same 7-11 bpm prediction error underneath.

### Equivalent race time (Riegel)
- Formula: T2 = T1 x (D2 / D1)^1.06
- Source: Riegel PS. Athletic records and human endurance. American Scientist. 1981;69(3):285-290.
- URL: https://pubmed.ncbi.nlm.nih.gov/7235349/
- Last checked: 2026-07-30
- Reported uncertainty: The 1.06 exponent was fitted to world-record performances from 100 m to 100 miles, and Riegel found it close to constant across events and across groups of runners. It assumes you are equally trained for both distances, and it is most optimistic exactly where it is most used: predicting a marathon from a short race, where the limit is fuelling and durability rather than speed. The tool therefore shows the prediction at 1.06 alongside 1.08 and 1.10 so it reads as a spread.

### Mile to kilometre conversion
- Formula: 1 mile = 1.609344 km (exact, by definition)
- Source: Thompson A, Taylor BN. Guide for the Use of the International System of Units (SI). NIST Special Publication 811, 2008 edition. National Institute of Standards and Technology.
- URL: https://www.nist.gov/pml/special-publication-811
- Last checked: 2026-07-30
- Reported uncertainty: None - the international mile is defined as exactly 1609.344 metres, so this conversion is exact and every rounding you see is ours, at the display edge only.

### Calories burned from METs
- Formula: kcal/min = MET x 3.5 x body mass (kg) / 200
- Source: Herrmann SD, Willis EA, Ainsworth BE, Barreira TV, Hastert M, Kracht CL, Schuna JM Jr, Cai Z, Quan M, Tudor-Locke C, Whitt-Glover MC, Jacobs DR. 2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities. J Sport Health Sci. 2024;13(1):6-12. doi:10.1016/j.jshs.2023.10.010
- URL: https://pacompendium.com/adult-compendium/
- Last checked: 2026-07-30
- Reported uncertainty: Three separate approximations stack here. Each MET value is a population mean measured in a lab on other people, and the Compendium publishes no per-row error term. The equation is GROSS: it includes the calories you would have spent at rest over the same minutes, which is why the tool also shows the net figure. And 1 MET = 3.5 mL O2/kg/min is itself a convention anchored to a reference adult, so it runs slightly high for heavier and older bodies.

### Lean body mass (Boer)
- Formula: men: LBM (kg) = 0.407 x weight(kg) + 0.267 x height(cm) - 19.2; women: LBM = 0.252 x weight + 0.473 x height - 48.3
- Source: Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984;247(4 Pt 2):F632-F636.
- URL: https://doi.org/10.1152/ajprenal.1984.247.4.F632
- Last checked: 2026-07-30
- Reported uncertainty: Derived to normalise body-fluid volumes, not to assess athletes. It knows only your height, weight and sex, so it cannot tell a heavily muscled body from a heavier one of the same dimensions - two people at the same height and weight get the same answer regardless of how that mass is distributed.

### Lean body mass (James)
- Formula: men: LBM (kg) = 1.10 x weight(kg) - 128 x (weight(kg) / height(cm))^2; women: LBM = 1.07 x weight - 148 x (weight / height)^2
- Source: James WPT. Research on Obesity: A Report of the DHSS/MRC Group. London: Her Majesty's Stationery Office; 1976. Equation as reproduced in: Comparison of ten predictive equations for estimating lean body mass with dual-energy X-ray absorptiometry in older patients. Br J Radiol. 2022;95(1133):20210378.
- URL: https://academic.oup.com/bjr/article/95/1133/20210378/7477377
- Last checked: 2026-07-30
- Reported uncertainty: The only one of the three with a non-linear shape term, so it diverges fastest from the others at the extremes of height and weight. The originating document is a 1976 government report rather than a journal paper, so the equation is verified here against its reproduction in a peer-reviewed comparison study, not against the report itself.

### Lean body mass (Hume)
- Formula: men: LBM (kg) = 0.32810 x weight(kg) + 0.33929 x height(cm) - 29.5336; women: LBM = 0.29569 x weight + 0.41813 x height - 43.2933
- Source: Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966;19(4):389-391. doi:10.1136/jcp.19.4.389
- URL: https://doi.org/10.1136/jcp.19.4.389
- Last checked: 2026-07-30
- Reported uncertainty: The earliest of the three and derived against total body water in a mid-1960s cohort, which is the likeliest reason it reads consistently lower than Boer and James at the same height and weight.

### Disagreement between published lean-mass equations
- Formula: spread across Boer, James and Hume at the same height, weight and sex: commonly 2-5 kg
- Source: Comparison of ten predictive equations for estimating lean body mass with dual-energy X-ray absorptiometry in older patients. Br J Radiol. 2022;95(1133):20210378.
- URL: https://academic.oup.com/bjr/article/95/1133/20210378/7477377
- Last checked: 2026-07-30
- Reported uncertainty: The spread between equations is a floor on the uncertainty, not the whole of it: all three share the same blindness to how mass is distributed, so they can agree with each other and still be some distance from a scan.

### Body fat from circumferences (Hodgdon & Beckett, the tape method)
- Formula: men: %BF = 86.010 x log10(abdomen - neck) - 70.041 x log10(height) + 36.76; women: %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387 (all measurements in inches)
- Source: Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. San Diego, CA: Naval Health Research Center; 1984. Report No. 84-11. Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. San Diego, CA: Naval Health Research Center; 1984. Report No. 84-29.
- URL: https://apps.dtic.mil/sti/html/tr/ADA146456/index.html
- Last checked: 2026-07-30
- Reported uncertainty: This site shows a +/-4 percentage-point band. // VERIFY: that figure is taken from secondary summaries reporting the method agrees with hydrostatic weighing to within roughly 3-4 points, deliberately using the wider edge; the Naval Health Research Center reports state their own standard error and the DTIC scans were not machine-readable when this pack was built. Read reports 84-11 and 84-29 and replace it with the published figure. Do not narrow it from memory. Separately, the method is sensitive to tape placement: a centimetre of drift at the abdomen moves the answer by close to a full point.

### Body fat from BMI (Deurenberg)
- Formula: %BF = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (sex: male 1, female 0)
- Source: Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr. 1991;65(2):105-114.
- URL: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/9C03B18E1A0E4CDB0441644EE64D9AA2/S0007114591000193a.pdf/body_mass_index_as_a_measure_of_body_fatness_age_and_sexspecific_prediction_formulas.pdf
- Last checked: 2026-07-30
- Reported uncertainty: The paper reports R^2 = 0.79 and a standard error of estimate of 4.1 percentage points in 1229 adults aged 7-83 with BMI 13.9-40.9. Four points is wide: at an estimate of 22% it means the honest reading is roughly 18-26%. Because the input is BMI, the equation cannot distinguish muscle from fat at all, so it reads high for heavily muscled bodies and low for lightly muscled ones.

### Waist-to-height ratio bands (NICE)
- Formula: waist / height: 0.4 to 0.49 healthy central adiposity, 0.5 to 0.59 increased central adiposity, 0.6 or more high central adiposity
- Source: National Institute for Health and Care Excellence. Overweight and obesity management. NICE guideline NG246. Section: Identifying and assessing overweight, obesity and central adiposity. NICE, accessed 2026-07-30.
- URL: https://www.nice.org.uk/guidance/ng246/chapter/Identifying-and-assessing-overweight-obesity-and-central-adiposity
- Last checked: 2026-07-30
- Reported uncertainty: NICE states these bands apply to adults with a BMI under 35 kg/m2, of both sexes and all ethnicities, including adults with high muscle mass. Above a BMI of 35 the ratio adds little. NICE does not define a category below 0.4, so neither does this site - the tool says the ratio is below the range NICE groups as healthy rather than inventing a label for it.

### One-rep max (Epley)
- Formula: 1RM = weight x (1 + reps / 30)
- Source: Epley B. Poundage Chart. In: Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985. Independently validated in: LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211-213.
- URL: https://www.unm.edu/~rrobergs/478PredictionAccuracy.pdf
- Last checked: 2026-07-30
- Reported uncertainty: The original source is a 1985 coaching chart, not a journal paper - there is no published derivation, only the equation and decades of independent testing of it. LeSuer and colleagues found mean prediction error within about 3% between 2 and 10 reps. Above 10 reps no published accuracy figure covers it, and Epley and Brzycki pull apart quickly: at 15 reps they differ by roughly 9% of the midpoint.
- Note: this is a field convention rather than a primary research finding.

### One-rep max (Brzycki)
- Formula: 1RM = weight x 36 / (37 - reps), equivalently weight / (1.0278 - 0.0278 x reps)
- Source: Brzycki M. Strength testing - predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88-90. doi:10.1080/07303084.1993.10606684
- URL: https://doi.org/10.1080/07303084.1993.10606684
- Last checked: 2026-07-30
- Reported uncertainty: Validated by LeSuer and colleagues in 1997 to within about 3% mean error at 2-10 reps. The equation has a hard mathematical limit: the denominator reaches zero at 37 reps, so the predicted max climbs towards infinity as rep counts get high, and it should not be read at all above roughly 12-15 reps. src/lib/health/strength.ts returns no value rather than a number once reps reach 37.

### One-rep-max prediction accuracy
- Formula: mean prediction error within about 3% at 2-10 repetitions; no published figure above 10
- Source: LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211-213.
- URL: https://journals.lww.com/nsca-jscr/abstract/1997/11000/the_accuracy_of_prediction_equations_for.2.aspx
- Last checked: 2026-07-30
- Reported uncertainty: The 3% figure is a mean across a study population on three barbell lifts; your own error on an unfamiliar movement, or on a set that stopped short of true failure, can be larger. Above 10 reps the validation simply does not reach, which is why the tool widens its language rather than quoting a number it does not have.

### Warm-up loading ladder
- Formula: 40% x 8, 55% x 5, 70% x 3, 85% x 2, 95% x 1 of the working weight
- Source: Percentages are a widely used training convention with no primary source. The rep-to-percentage relationship they lean on is Brzycki M. Strength testing - predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88-90.
- URL: https://doi.org/10.1080/07303084.1993.10606684
- Last checked: 2026-07-30
- Reported uncertainty: No study prescribes these particular percentages, and the site says so on the page. What the ladder is genuinely good for is arithmetic: five percentages of your working weight, rounded to a load you can actually build on a bar with the plates most gyms stock. The only part of the pattern every strength text agrees on is that reps descend as load climbs.
- Note: this is a field convention rather than a primary research finding.

### Estimated due date from the last menstrual period
- Formula: EDD = first day of LMP + 280 days
- Source: American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154.
- URL: https://doi.org/10.1097/AOG.0000000000002046
- Last checked: 2026-07-30
- Reported uncertainty: ACOG states this convention assumes a regular 28-day cycle with ovulation on day 14, and does not account for inaccurate recall of the last period, irregular cycle length, or variation in when ovulation actually happened. ACOG treats a first-trimester ultrasound as the most accurate way to establish gestational age, and reports that about half of women recall their last period accurately.

### Cycle-length adjustment to the due date
- Formula: EDD = LMP + 280 days + (cycle length - 28)
- Source: American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154. The 28-day cycle and day-14 ovulation assumption is stated in the opinion; the arithmetic shift for a different cycle length is derived from it.
- URL: https://doi.org/10.1097/AOG.0000000000002046
- Last checked: 2026-07-30
- Reported uncertainty: A derived adjustment, not an ACOG recommendation. It assumes the whole difference in cycle length falls in the follicular phase, which is where Bull 2019 found most of the variation, but the luteal phase varies too.
- Note: this is a field convention rather than a primary research finding.

### Estimated conception date from the due date
- Formula: conception date = EDD - 266 days
- Source: American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154. 266 days follows from the opinion's stated 280-day convention and its day-14 ovulation assumption (280 - 14).
- URL: https://doi.org/10.1097/AOG.0000000000002046
- Last checked: 2026-07-30
- Reported uncertainty: The result is a window, not a day. Sperm can survive several days in the reproductive tract, so intercourse days earlier can produce a conception dated here, and ovulation timing itself varies.
- Note: this is a field convention rather than a primary research finding.

### Gestational age in weeks and days
- Formula: gestational age (days) = 280 - days until EDD
- Source: American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154.
- URL: https://doi.org/10.1097/AOG.0000000000002046
- Last checked: 2026-07-30
- Reported uncertainty: Inherits every uncertainty of the due date it is measured from. Trimester boundaries (13w6d and 27w6d) are a widely used convention rather than a finding.
- Note: this is a field convention rather than a primary research finding.

### Estimated ovulation day, anchored to the luteal phase
- Formula: ovulation day of cycle = cycle length - 14
- Source: American College of Obstetricians and Gynecologists. Fertility Awareness-Based Methods of Family Planning. ACOG patient FAQ, accessed 2026. States that in an average 28-day menstrual cycle, ovulation occurs about 14 days before the start of the next menstrual period.
- URL: https://www.acog.org/womens-health/faqs/fertility-awareness-based-methods-of-family-planning
- Last checked: 2026-07-30
- Reported uncertainty: Counted back from the next expected period rather than forward from the last one, because the follicular phase is what varies. The NHS puts ovulation at 10 to 16 days before the next period, and Bull 2019 measured a mean luteal phase of 12.4 days with a 95% interval of 7 to 17 days, so this is a midpoint of a week-wide window.
- Note: this is a field convention rather than a primary research finding.

### Fertile window (ACOG patient guidance)
- Formula: fertile window = ovulation - 5 days through ovulation + 1 day
- Source: American College of Obstetricians and Gynecologists. Fertility Awareness-Based Methods of Family Planning. ACOG patient FAQ, accessed 2026. States that pregnancy can result from sex anywhere from 5 days before ovulation until 1 day after ovulation.
- URL: https://www.acog.org/womens-health/faqs/fertility-awareness-based-methods-of-family-planning
- Last checked: 2026-07-30
- Reported uncertainty: The window is drawn around an estimated ovulation date, so it is only as good as that estimate. Widening it is the honest response to an uncertain ovulation date; narrowing it is not.

### The six-day conception window
- Formula: conceptions occurred only from intercourse in the 6 days ending on the day of ovulation
- Source: Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby. N Engl J Med. 1995;333(23):1517-1521.
- URL: https://doi.org/10.1056/NEJM199512073332301
- Last checked: 2026-07-30
- Reported uncertainty: 221 women, 625 cycles. Per-day probability of conception ranged from about 0.10 five days before ovulation to about 0.33 on the day of ovulation itself, so days inside the window are not equivalent to each other.

### Implantation window after ovulation
- Formula: implantation occurred 6 to 12 days after ovulation; 84% on day 8, 9 or 10
- Source: Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-1799.
- URL: https://doi.org/10.1056/NEJM199906103402304
- Last checked: 2026-07-30
- Reported uncertainty: Implantation was dated by the first appearance of chorionic gonadotropin in daily urine samples, in 189 pregnancies. It is a hormone measurement, not a sensation, and the study reports nothing about symptoms.

### hCG doubling time
- Formula: doubling time = (hours between draws x ln 2) / ln(second value / first value)
- Source: Barnhart KT, Sammel MD, Rinaudo PF, Zhou L, Hummel AC, Guo W. Symptomatic patients with an early viable intrauterine pregnancy: HCG curves redefined. Obstet Gynecol. 2004;104(1):50-55. The arithmetic is the exponential-growth identity; this citation is for the clinical framing the calculator uses.
- URL: https://doi.org/10.1097/01.AOG.0000128174.48843.12
- Last checked: 2026-07-30
- Reported uncertainty: The identity assumes a constant rate of change between the two draws. Real hCG rises more slowly as the level gets higher, so a doubling time measured at 1,200 mIU/mL is not comparable to one measured at 120. Assay-to-assay variation also means two values should ideally come from the same laboratory.
- Note: this is a field convention rather than a primary research finding.

### Slowest hCG rise seen with a viable intrauterine pregnancy
- Formula: minimum rise: 24% at 1 day, 53% at 2 days
- Source: Barnhart KT, Sammel MD, Rinaudo PF, Zhou L, Hummel AC, Guo W. Symptomatic patients with an early viable intrauterine pregnancy: HCG curves redefined. Obstet Gynecol. 2004;104(1):50-55.
- URL: https://doi.org/10.1097/01.AOG.0000128174.48843.12
- Last checked: 2026-07-30
- Reported uncertainty: Derived from 287 symptomatic women (pain or bleeding, non-diagnostic ultrasound) who went on to have a viable intrauterine pregnancy. It is the slowest rise observed in that group, not a threshold anyone passes or fails, and it does not apply in reverse.

### Real-world cycle and luteal phase variation
- Formula: mean cycle 29.3 days; 13% of cycles exactly 28 days; mean luteal phase 12.4 days (95% CI 7-17)
- Source: Bull JR, Rowland SP, Scherwitzl EB, Scherwitzl R, Danielsson KG, Harper J. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ Digit Med. 2019;2:83.
- URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC6710244/
- Last checked: 2026-07-30
- Reported uncertainty: 612,613 cycles from 124,648 users of a fertility app, so the population self-selects towards people tracking closely. The direction of the finding -- that the textbook 28-day cycle is a minority -- is not in doubt.

### Gestational weight gain ranges (IOM 2009)
- Formula: total gain by pre-pregnancy BMI: 12.5-18 kg, 11.5-16 kg, 7-11.5 kg, 5-9 kg
- Source: Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: The National Academies Press; 2009. Table S-1, New recommendations for total and rate of weight gain during pregnancy, by prepregnancy BMI.
- URL: https://www.nationalacademies.org/read/12584/chapter/2
- Last checked: 2026-07-30
- Reported uncertainty: Population ranges for a pregnancy overall, not a target for any individual week. The report's own rate calculations assume a first-trimester gain of 0.5-2 kg (1.1-4.4 lb). The twin ranges are described by the report as provisional, and the report gives no range at all for a twin pregnancy beginning underweight.

### Mid-parental (target) height
- Formula: boys: ((mother + 13) + father) / 2 cm; girls: ((father - 13) + mother) / 2 cm
- Source: Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2-9 years allowing for heights of parents. Arch Dis Child. 1970;45(244):755-762.
- URL: https://pubmed.ncbi.nlm.nih.gov/5491878/
- Last checked: 2026-07-30
- Reported uncertainty: Tanner's band of +/- 8.5 cm around the estimate spans the 3rd to 97th centile of expected adult height, so the honest answer is a 17 cm range. Later work widened the band further, to about +/- 9 cm for girls and +/- 10 cm for boys. The estimate also assumes a population like the one it was derived from and takes no account of the child's own measured growth, nutrition or health.

### LMS z-score (Cole)
- Formula: Z = ((X / M)^L - 1) / (L x S), and Z = ln(X / M) / S when L = 0
- Source: Cole TJ. The LMS method for constructing normalized growth standards. Eur J Clin Nutr. 1990;44(1):45-60.
- URL: https://pubmed.ncbi.nlm.nih.gov/2354692/
- Last checked: 2026-07-30
- Reported uncertainty: The z-score is exact arithmetic given L, M and S; all of the uncertainty lives in the reference table those three come from, and in whether that table describes the child in front of you.

### Centile from a z-score
- Formula: centile = 100 x standard normal CDF of Z
- Source: Cole TJ. The LMS method for constructing normalized growth standards. Eur J Clin Nutr. 1990;44(1):45-60. The LMS transformation is designed so that the transformed measurement is standard normal, which is what makes the centile the normal CDF of the z-score.
- URL: https://pubmed.ncbi.nlm.nih.gov/2354692/
- Last checked: 2026-07-30
- Reported uncertainty: The normal CDF is evaluated with the Zelen and Severo rational approximation (Abramowitz and Stegun 26.2.17, absolute error under 7.5e-8) and inverted with Acklam's approximation (relative error under 1.15e-9). Both are far more precise than the tenth of a centile anything here displays.
- Note: this is a field convention rather than a primary research finding.

### Name popularity rank and count (ONS)
- Formula: rank and count per name, per sex, per year, exactly as the ONS publishes them
- Source: Office for National Statistics. Baby names in England and Wales: from 1996 (1996 to 2025). Table 1, names for baby girls; Table 2, names for baby boys. Contains public sector information licensed under the Open Government Licence v3.0.
- URL: https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/livebirths/datasets/babynamesinenglandandwalesfrom1996
- Last checked: 2026-07-30
- Reported uncertainty: England and Wales only. The ONS publishes names with a count of three or more, so rarer names are absent from the source itself. A rank is a position in one jurisdiction in one year and says nothing about a name anywhere else.

### Name style tags, derived from published ranks
- Formula: top-100: rank <= 100 now; popular: 101-500; uncommon: 501+; rising/falling: rank moved 100+ places over 5 years with both ranks inside the top 1000; enduring: top 200 in both 1996 and now; revival: outside the top 500 in 1996 and inside the top 200 now; vintage: top 100 in 1996 and outside the top 500 now
- Source: Derived arithmetically from Office for National Statistics, Baby names in England and Wales: from 1996 (1996 to 2025). The rules are arithmetic on published ranks, not editorial judgements, and each rule is printed in public/data/names/index.json so any name can be checked against the ONS table.
- URL: https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/livebirths/datasets/babynamesinenglandandwalesfrom1996
- Last checked: 2026-07-30
- Reported uncertainty: These are labels for movements in a popularity table, not descriptions of what a name is like. A name can be tagged rising because a hundred more families chose it, which is a fact about a year rather than a quality of the name.
- Note: this is a field convention rather than a primary research finding.

### First-year cost, summed from published figures
- Formula: total = sum of the published annual figures selected, each shown with the year its money is expressed in
- Source: Child Care Aware of America. Child Care in America: 2025 Price and Supply. Published May 2026. The summation itself is arithmetic; every input is a published figure stored in src/data/packs/baby-costs.json with its own source and currency year.
- URL: https://info.childcareaware.org/price-and-supply-2025
- Last checked: 2026-07-30
- Reported uncertainty: A sum of national averages is not a forecast of a household. Child care prices in particular vary by a factor of three across US states, and figures from different years are not made comparable by adding them - this tool shows each currency year rather than converting them into a common one.
- Note: this is a field convention rather than a primary research finding.

### US child care prices, 2025 (Child Care Aware of America)
- Formula: infant, center $15,636/yr; infant, family child care home $11,673/yr; national average across ages and settings $13,184/yr
- Source: Child Care Aware of America. Child Care in America: 2025 Price and Supply. Published May 2026. National average calculated by averaging three methods across the 47 states for which CCAoA had price data; the infant and four-year-old figures quoted here are from the Average of Averages method.
- URL: https://info.childcareaware.org/price-and-supply-2025
- Last checked: 2026-07-30
- Reported uncertainty: National averages across 47 states. CCAoA's own state tables for 2024 run from roughly $8,600 to over $26,000 a year for infant center care, so the national figure describes the country and not a county. CCAoA publishes no toddler figure in the 2025 national tables, so none is shown or interpolated.

### USDA expenditures on a child aged 0 to 2 (2015 dollars)
- Formula: middle-income married-couple family, two children: $12,680 a year at age 0-2; $9,690 lowest income group, $19,770 highest
- Source: Lino M, Kuczynski K, Rodriguez N, Schap T. Expenditures on Children by Families, 2015. US Department of Agriculture, Center for Nutrition Policy and Promotion. Miscellaneous Report No. 1528-2015, January 2017, revised March 2017. Table 1, estimated annual expenditures on a child by married-couple families, overall United States.
- URL: https://www.fns.usda.gov/research/cnpp/expenditures-children-families
- Last checked: 2026-07-30
- Reported uncertainty: Expressed in 2015 dollars and not adjusted forward here. USDA's own page states that the most recent version of the report was published in 2017 and estimates the cost of raising children born in 2015, and that USDA is evaluating the methods used to inform the report; there has been no newer edition since.

### Time-restricted eating window (clock arithmetic)
- Formula: window opens = last meal + fasting hours; window closes = opens + eating hours
- Source: de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2019;381(26):2541-2551. doi:10.1056/NEJMra1905136
- URL: https://pubmed.ncbi.nlm.nih.gov/31881139/
- Last checked: 2026-07-30
- Reported uncertainty: There is no uncertainty in the arithmetic - it is addition on a clock. The uncertainty is entirely in what a schedule does for any individual, which this calculator does not estimate and does not claim.
- Note: this is a field convention rather than a primary research finding.

### Lifestyle life-expectancy differences, summed (this site's construction)
- Formula: estimate = chronological age - sum of published life-expectancy differences, clamped to +/- 12 years
- Source: Terms: Jha P, et al. N Engl J Med. 2013;368(4):341-350 (smoking). Moore SC, et al. PLoS Med. 2012;9(11):e1001335 (physical activity). Fadnes LT, et al. PLoS Med. 2022;19(2):e1003889 (diet). Wood AM, et al. Lancet. 2018;391(10129):1513-1523 (alcohol). Prospective Studies Collaboration. Lancet. 2009;373(9669):1083-1096 (body-mass index).
- URL: https://myhealthmywellness.com/methodology
- Last checked: 2026-07-30
- Reported uncertainty: Large, and structural rather than statistical. Each term is a life-expectancy difference its own study published in years, but the terms come from different cohorts with different reference groups and different starting ages, and their effects overlap heavily through shared cardiovascular and metabolic pathways. Adding them therefore overstates the combined difference by an amount no publication quantifies. The result is reported as a range, clamped to plus or minus 12 years, and always shown broken down by term.
- Note: this is a field convention rather than a primary research finding.

## Sections

- [Body & Fitness](https://myhealthmywellness.com/body-fitness): Metabolism, nutrition targets, heart, and training — every number cited.
- [Cycle & Fertility](https://myhealthmywellness.com/cycle-fertility): Period, ovulation, conception, and early-pregnancy hormones — private, client-side only.
- [Pregnancy & Baby](https://myhealthmywellness.com/pregnancy-baby): Week by week through the registry — sourced from ACOG and NHS patient guidance.

## Calculators

- [A1C calculator](https://myhealthmywellness.com/a1c-calculator): An A1C calculator converts a hemoglobin A1C percentage into an estimated average glucose, in both mg/dL and mmol/L, using the ADA equation eAG = 28.7 x A1C - 46.7 published by Nathan in 2008.
- [Glucose to A1C calculator](https://myhealthmywellness.com/glucose-to-a1c-calculator): This converts an average blood glucose reading into the A1C percentage it corresponds to, by inverting the ADA equation from the ADAG study.
- [GMI calculator](https://myhealthmywellness.com/gmi-calculator): GMI estimates what an A1C would look like given your CGM mean glucose, using the equation GMI = 3.31 + 0.02392 x mean glucose from Bergenstal 2018.
- [TDEE calculator](https://myhealthmywellness.com/tdee-calculator): Your TDEE is the calories you burn in a day: a resting metabolic rate from the Mifflin-St Jeor equation, multiplied by an activity factor.
- [BMR calculator](https://myhealthmywellness.com/bmr-calculator): BMR is the energy your body uses at complete rest.
- [Maintenance calorie calculator](https://myhealthmywellness.com/maintenance-calorie-calculator): Maintenance calories are the same quantity as TDEE, under a different name: the energy that leaves your weight where it is.
- [Calorie deficit calculator](https://myhealthmywellness.com/calorie-deficit-calculator): A calorie deficit is the gap between the energy you use and the energy you eat.
- [Weight loss calculator](https://myhealthmywellness.com/weight-loss-calculator): This projects weight change from a daily calorie deficit as a range, not a single figure and not a date.
- [Macro calculator](https://myhealthmywellness.com/macro-calculator): This turns a daily calorie figure into grams of protein, carbohydrate and fat using the Atwater factors of 4, 4 and 9 kcal per gram.
- [Protein calculator](https://myhealthmywellness.com/protein-calculator): Four organisations have published protein ranges: the RDA of 0.8 g per kg from the IOM, 1.2 to 2.0 for athletes in the 2016 ACSM joint statement, 1.4 to 2.0 from the ISSN, and 1.0 to 1.2 for healthy over-65s from PROT-AGE.
- [Water intake calculator](https://myhealthmywellness.com/water-intake-calculator): The eight-glasses rule is about 1.9 litres of drinking water and nobody published it.
- [Max heart rate calculator](https://myhealthmywellness.com/max-heart-rate-calculator): A maximum heart rate calculator estimates the fastest your heart beats at all-out effort.
- [Heart rate zone calculator](https://myhealthmywellness.com/heart-rate-zone-calculator): A heart rate zone calculator turns your age into five training bands: 50 to 60 percent of maximum through 90 to 100 percent.
- [Lean body mass calculator](https://myhealthmywellness.com/lean-body-mass-calculator): A lean body mass calculator estimates how much of your weight is not fat, from your height, weight and sex.
- [Body fat calculator](https://myhealthmywellness.com/body-fat-calculator): A body fat calculator estimates what share of your weight is fat.
- [One rep max calculator](https://myhealthmywellness.com/one-rep-max-calculator): A one rep max calculator predicts the heaviest single you could lift from a set you actually completed.
- [Pace calculator](https://myhealthmywellness.com/pace-calculator): A running pace calculator converts a finish time and a distance into pace per kilometre and per mile, with even splits for every marker including the fractional last one.
- [Calories burned calculator](https://myhealthmywellness.com/calories-burned-calculator): A calories burned calculator multiplies an activity's MET value by your body weight and duration, using the equation kcal per minute equals MET times 3.5 times kilograms divided by 200.
- [Intermittent fasting calculator](https://myhealthmywellness.com/intermittent-fasting-calculator): This works out when a time-restricted eating window opens and closes from the time of your last meal, for 16:8, 18:6, 20:4 and one meal a day.
- [Biological age calculator](https://myhealthmywellness.com/biological-age-calculator): This adds up life-expectancy differences that five studies published in years - for smoking, activity, diet, alcohol and body weight - and subtracts them from your age.
- [Period calculator](https://myhealthmywellness.com/period-calculator): A period calculator projects your next period dates from the first day of your last one and your average cycle length.
- [Ovulation calculator](https://myhealthmywellness.com/ovulation-calculator): This ovulation calculator counts back from your next expected period rather than forward from your last one, because the first half of the cycle is what varies.
- [Conception date calculator](https://myhealthmywellness.com/conception-date-calculator): A conception date calculator subtracts 266 days from an estimated due date, or adds 14 days to the first day of a last period, following the convention ACOG publishes.
- [Implantation calculator](https://myhealthmywellness.com/implantation-calculator): An implantation calculator dates the window in which a pregnancy implants, from your estimated ovulation date.
- [hCG doubling time calculator](https://myhealthmywellness.com/hcg-doubling-calculator): This works out the doubling time between two hCG results and the percentage change between them, using the interval you enter.
- [Due date calculator](https://myhealthmywellness.com/due-date-calculator): A due date calculator adds 280 days to the first day of your last period, the convention ACOG publishes, and shifts it when your cycle is not 28 days long.
- [Pregnancy weight gain calculator](https://myhealthmywellness.com/pregnancy-weight-gain-calculator): This applies the 2009 Institute of Medicine ranges: it works out your pre-pregnancy BMI, names the category the IOM puts that in, and shows the total gain range for the whole pregnancy plus the cumulative range by the week you enter.
- [Child height predictor](https://myhealthmywellness.com/height-predictor): A child height predictor applies Tanner's mid-parental method: add 13 centimetres to the mother's height for a boy, or subtract it from the father's for a girl, then average the two.
- [Growth percentile calculator](https://myhealthmywellness.com/growth-percentile-calculator): A growth percentile calculator turns a child's height or weight into a centile using the LMS method Cole published in 1990, with the reference tables the WHO and CDC publish by age and sex.
- [Baby name generator](https://myhealthmywellness.com/baby-name-generator): This baby name generator filters 4,122 names from the Office for National Statistics record of every name given in England and Wales since 1996.
- [Baby cost calculator](https://myhealthmywellness.com/baby-cost-calculator): This first-year baby cost calculator adds up published figures rather than estimates: Child Care Aware of America 2025 child care prices, the National Diaper Bank Network nappy range, and the USDA 2015 age nought to two total.
- [My Numbers Log](https://myhealthmywellness.com/numbers-log): The Numbers Log keeps eight to ten body metrics on one card and asks you to re-take them four times a year, so you are reading a trend rather than a single figure.
- [Which numbers matter](https://myhealthmywellness.com/which-numbers-matter): This sorts body metrics into screen, track and act using the checking intervals that named bodies such as the USPSTF, the ADA and NICE actually publish, plus whatever you say you are already working on.

## Reference pages

- [A1C chart: A1C to average blood sugar](https://myhealthmywellness.com/a1c-chart)
- [A1C to average glucose: the formula and what it means](https://myhealthmywellness.com/a1c-to-average-glucose)
- [What is a good A1C? The ranges the ADA actually defines](https://myhealthmywellness.com/what-is-a-good-a1c)
- [How to calculate A1C from average glucose](https://myhealthmywellness.com/how-to-calculate-a1c)
- [How much can A1C change in 3 months?](https://myhealthmywellness.com/how-much-can-a1c-change-in-3-months)
- [Target heart rate by age](https://myhealthmywellness.com/target-heart-rate-by-age)
- [Zone 2 heart rate, explained](https://myhealthmywellness.com/zone-2-explained)
- [Max heart rate formulas compared: Fox, Tanaka and Gulati](https://myhealthmywellness.com/max-heart-rate-formulas-compared)
- [How TDEE is calculated](https://myhealthmywellness.com/how-tdee-is-calculated)
- [Why TDEE calculators disagree](https://myhealthmywellness.com/why-tdee-calculators-disagree)
- [How much protein per day](https://myhealthmywellness.com/how-much-protein-per-day)
- [Body fat percentage vs BMI](https://myhealthmywellness.com/body-fat-vs-bmi)
- [Lean body mass formulas compared: Boer, James and Hume](https://myhealthmywellness.com/lean-body-mass-formulas-compared)
- [How accurate are due date calculators?](https://myhealthmywellness.com/how-accurate-are-due-date-calculators)
- [Implantation timing, explained](https://myhealthmywellness.com/implantation-timing-explained)

## Glossary

- [A1C](https://myhealthmywellness.com/glossary/a1c): A1C is the proportion of your haemoglobin that has become glycated, reported as a percentage, and it reflects average glucose exposure over roughly the previous two to three months. It is a weighted average rather than an even one, because the most recent weeks contribute more than the earliest.
- [eAG (estimated average glucose)](https://myhealthmywellness.com/glossary/eag): eAG is an average blood glucose figure calculated from an A1C result, using the regression published by the ADAG study in 2008. The word "estimated" is load-bearing: it comes from a population fit, and individuals at the same A1C had meaningfully different real averages.
- [GMI (glucose management indicator)](https://myhealthmywellness.com/glossary/gmi): GMI estimates an A1C-like percentage from continuous glucose monitoring data. It was named in 2018 specifically to stop CGM-derived figures being called "estimated A1C", because the two commonly differ within the same person and that difference is informative rather than an error.
- [IFCC units (mmol/mol)](https://myhealthmywellness.com/glossary/ifcc-units): IFCC units express A1C as millimoles of glycated haemoglobin per mole of total haemoglobin, rather than as a percentage. Laboratories in the UK, Australia and much of Europe report this instead of the NGSP percentage used in the US, Canada and India.
- [NGSP](https://myhealthmywellness.com/glossary/ngsp): The National Glycohemoglobin Standardization Program certifies A1C assay methods against a reference method. Its certification criteria are the reason a small difference between two A1C results may be the test rather than a change in you.
- [BMR (basal metabolic rate)](https://myhealthmywellness.com/glossary/bmr): BMR is the energy your body uses at complete rest to keep basic functions running. In practice almost nobody measures it directly; the figures you see are estimates from a prediction equation fitted to a study population.
- [RMR (resting metabolic rate)](https://myhealthmywellness.com/glossary/rmr): RMR is energy expenditure at rest but under less strict conditions than BMR — you have not necessarily fasted overnight or lain still in a dark room. It usually reads slightly higher than BMR, and the two terms are frequently used interchangeably even though they are not identical.
- [TDEE (total daily energy expenditure)](https://myhealthmywellness.com/glossary/tdee): TDEE is everything you spend in a day: your resting rate, the energy cost of digesting food, deliberate exercise, and all the incidental movement in between. The usual estimate multiplies a BMR estimate by an activity factor.
- [NEAT (non-exercise activity thermogenesis)](https://myhealthmywellness.com/glossary/neat): NEAT is all the energy you spend moving that is not deliberate exercise: walking to the shop, fidgeting, standing, carrying things, pacing on the phone. It varies enormously between people and is the main reason two people with the same workout routine can have very different daily expenditure.
- [Maintenance calories](https://myhealthmywellness.com/glossary/maintenance-calories): Maintenance calories is another name for your TDEE: the intake at which body weight is, on average, stable. It is not a fixed number — it moves with weight, activity and time.
- [Calorie deficit](https://myhealthmywellness.com/glossary/calorie-deficit): A calorie deficit is intake below expenditure. The familiar rule of thumb that 3,500 kcal equals a pound comes from a 1958 paper and systematically overestimates long-run loss, because expenditure itself falls as body mass falls.
- [MET (metabolic equivalent of task)](https://myhealthmywellness.com/glossary/met): One MET is the energy cost of sitting quietly, defined as 3.5 mL of oxygen per kilogram per minute. An activity rated at 8 METs costs roughly eight times that, which lets any activity be converted into calories for a given body weight and duration.
- [HRmax (maximum heart rate)](https://myhealthmywellness.com/glossary/hrmax): HRmax is the highest rate your heart can beat during maximal effort. Every age-based formula for it is an estimate with substantial individual scatter, and the common ones disagree with each other by more as age rises.
- [Heart-rate reserve](https://myhealthmywellness.com/glossary/heart-rate-reserve): Heart-rate reserve is the gap between your resting heart rate and your maximum. Using it, rather than maximum alone, produces training zones that account for how fit you already are.
- [Karvonen method](https://myhealthmywellness.com/glossary/karvonen): The Karvonen method sets a target heart rate from your heart-rate reserve rather than from maximum alone: target = (HRmax − resting) × intensity + resting. Published in 1957, it is still the standard way to produce zones that reflect resting fitness.
- [Zone 2](https://myhealthmywellness.com/glossary/zone-2): Zone 2 is the second of five commonly used training bands, roughly 60–70% of maximum heart rate — an effort you could hold while talking in full sentences. The zone boundaries themselves are a field convention, and different bodies draw them differently.
- [Resting heart rate](https://myhealthmywellness.com/glossary/resting-heart-rate): Resting heart rate is your heart rate at complete rest, ideally measured before getting up. It costs nothing to measure and its own trend over months is more informative than any single reading.
- [Lean body mass](https://myhealthmywellness.com/glossary/lean-body-mass): Lean body mass is total body weight minus fat mass: muscle, bone, organs, water. The common equations estimate it from height and weight, and the three most-used ones disagree by several kilograms for the same person.
- [FFM (fat-free mass)](https://myhealthmywellness.com/glossary/ffm): Fat-free mass is everything in the body that is not fat. It is often used interchangeably with lean body mass, though strictly LBM includes the small amount of essential fat within organs and cell membranes while FFM excludes all fat.
- [Body fat percentage](https://myhealthmywellness.com/glossary/body-fat-percentage): Body fat percentage is fat mass as a share of total body weight. Every field method estimates it indirectly, and the error bars are wide enough that small changes between measurements are usually not real changes.
- [BMI (body mass index)](https://myhealthmywellness.com/glossary/bmi): BMI is weight in kilograms divided by height in metres squared. It was designed to describe populations, not individuals, and it cannot distinguish muscle from fat or say anything about where body fat sits.
- [Waist-to-height ratio](https://myhealthmywellness.com/glossary/waist-to-height-ratio): Waist-to-height ratio is waist circumference divided by height, in the same units. NICE recommends it alongside BMI with a memorable rule: keep your waist to less than half your height.
- [1RM (one-rep max)](https://myhealthmywellness.com/glossary/one-rep-max): Your one-rep max is the heaviest weight you could lift once with good form. Estimating it from a set of several reps avoids the risk of a true maximal attempt, at the cost of accuracy that falls as rep count rises.
- [RPE (rate of perceived exertion)](https://myhealthmywellness.com/glossary/rpe): RPE is a self-reported effort rating, commonly on a 1–10 scale where 10 is a maximal effort. It is subjective by design, which is both its weakness and the reason it adapts to days when you are tired or unwell.
- [AMDR (acceptable macronutrient distribution range)](https://myhealthmywellness.com/glossary/amdr): The AMDR is the range of intakes for each macronutrient associated with adequate nutrition, expressed as a share of total energy: protein 10–35%, fat 20–35%, carbohydrate 45–65% for adults.
- [Atwater factors](https://myhealthmywellness.com/glossary/atwater-factors): The Atwater factors are the conventional energy values used to convert nutrients into calories: 4 kcal per gram of protein, 4 for carbohydrate, 9 for fat, and 7 for alcohol.
- [DRI (dietary reference intakes)](https://myhealthmywellness.com/glossary/dri): The DRIs are a set of reference values for nutrient intake published by the National Academies, including the RDA, the AI, the EAR and the AMDR. They describe population reference points rather than personal prescriptions.
- [RDA (recommended dietary allowance)](https://myhealthmywellness.com/glossary/rda): The RDA is the average daily intake sufficient to meet the requirements of nearly all — about 97–98% of — healthy people in a group. It is deliberately set above the average requirement, so it is not a target most individuals must hit exactly.
- [EAR (estimated average requirement)](https://myhealthmywellness.com/glossary/ear): The EAR is the intake estimated to meet the requirement of half the healthy individuals in a group. It sits below the RDA and is used mainly for assessing the adequacy of group intakes rather than individual diets.
- [AI (adequate intake)](https://myhealthmywellness.com/glossary/ai): An AI is used where the evidence is insufficient to set an RDA: it is an observed or approximated intake assumed to be adequate. Water is the well-known example, which is why hydration guidance is softer than it sounds.
- [Total water intake](https://myhealthmywellness.com/glossary/total-water-intake): Total water intake counts all water consumed: drinks of every kind plus the water contained in food, which typically supplies around 20% of the total. Guidance figures refer to this total, not to plain water alone.
- [Naegele's rule](https://myhealthmywellness.com/glossary/naegele-rule): Naegele's rule estimates a due date as 280 days from the first day of the last menstrual period. It assumes a 28-day cycle with ovulation on day 14, so it can be adjusted when a cycle is reliably longer or shorter.
- [LMP (last menstrual period)](https://myhealthmywellness.com/glossary/lmp): The LMP is the first day of your most recent period, and it is the anchor date for most pregnancy dating. It is used because it is usually known, not because it is the most biologically precise starting point.
- [EDD (estimated due date)](https://myhealthmywellness.com/glossary/edd): The EDD is the date 40 weeks from the LMP. It is a midpoint of a distribution rather than an appointment: most births happen in a window of weeks around it, and ultrasound dating often revises it.
- [Gestational age](https://myhealthmywellness.com/glossary/gestational-age): Gestational age is how far a pregnancy has progressed, counted in completed weeks and days from the LMP. It runs about two weeks ahead of fetal age, which counts from conception.
- [DPO (days past ovulation)](https://myhealthmywellness.com/glossary/dpo): DPO counts days since ovulation and is the frame used for early-pregnancy timing, because it is anchored to the event that matters rather than to the previous period.
- [Fertile window](https://myhealthmywellness.com/glossary/fertile-window): The fertile window is the span of days in a cycle when intercourse can result in pregnancy: about five days before ovulation through the day after, reflecting how long sperm and egg survive.
- [Ovulation](https://myhealthmywellness.com/glossary/ovulation): Ovulation is the release of an egg from the ovary, roughly 14 days before the next period rather than 14 days after the last one. Anchoring it to the end of the cycle is why cycle length changes the estimate.
- [Luteal phase](https://myhealthmywellness.com/glossary/luteal-phase): The luteal phase runs from ovulation to the start of the next period. It is the more consistent half of the cycle, typically 9 to 17 days, which is why cycle-length variation mostly comes from the phase before it.
- [Follicular phase](https://myhealthmywellness.com/glossary/follicular-phase): The follicular phase runs from the first day of a period to ovulation. It is the variable half of the cycle, and most differences in total cycle length between people and between months happen here.
- [Implantation](https://myhealthmywellness.com/glossary/implantation): Implantation is when a fertilised egg embeds in the uterine lining, which is when hCG production begins and therefore when a pregnancy becomes detectable.
- [hCG (human chorionic gonadotropin)](https://myhealthmywellness.com/glossary/hcg): hCG is the hormone produced after implantation and measured by pregnancy tests. In early pregnancy its level rises quickly, and clinicians look at the rate of rise between two measurements rather than at any single value.
- [IOM weight-gain ranges](https://myhealthmywellness.com/glossary/iom-weight-gain-ranges): The Institute of Medicine's 2009 guidelines give recommended total pregnancy weight-gain ranges by pre-pregnancy BMI category, along with weekly rates for the second and third trimesters.
- [Mid-parental height](https://myhealthmywellness.com/glossary/mid-parental-height): Mid-parental height estimates a child's adult height from the parents' heights, adjusted by sex. Published by Tanner in 1970, it is a rough predictor with a wide honest range around it.
- [Percentile](https://myhealthmywellness.com/glossary/percentile): A percentile is a position within a reference population: the 25th percentile means 25% of that population sits below the value. It is a description of where someone stands, not a grade or a target.
- [Z-score](https://myhealthmywellness.com/glossary/z-score): A Z-score expresses how many standard deviations a value sits from the reference mean. Zero is exactly average; +1.88 corresponds to roughly the 97th percentile.
- [LMS method](https://myhealthmywellness.com/glossary/lms-method): The LMS method describes a growth reference using three age-specific parameters — L for skewness, M for the median and S for variation — which together allow any measurement to be converted into a Z-score and a percentile.

## Machine access

- Methodology: https://myhealthmywellness.com/methodology
- Data changelog: https://myhealthmywellness.com/changelog
- Verified data packs (JSON): https://myhealthmywellness.com/data/
- MCP server and developer docs: https://myhealthmywellness.com/developers
- Sitemap: https://myhealthmywellness.com/sitemap.xml

## Out of scope here (deliberately)

- Sleep and stress tools: https://theballastprinciple.com
- Pet calculators: https://routinetoolkit.com
- Money and tax calculators: https://budgetbuildinvest.com
- Recipe and kitchen maths: https://recipesandmeasures.com

## Contact

- support.cosyslabs@gmail.com