Body & Fitness
These are the numbers that describe how your body spends energy, moves blood, and uses protein and water. Each one is computed from a published formula that is named and linked on the page, with the honest error band the original paper reported. Start anywhere; every result points at the number it feeds into next.
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. It converts in either direction, shows IFCC units, and states which range the ADA defines your figure as falling in.
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. Enter a meter or CGM average in mg/dL or mmol/L and it returns the equivalent A1C in both NGSP percent and IFCC units, with the ADA range named.
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. Enter your mean glucose and, optionally, your laboratory A1C to see the gap between them, which the paper treats as informative rather than an error.
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. This calculator shows both, brackets the answer with the 10 percent error the equations carry, and names where your chosen activity factor sits against the FAO/WHO/UNU activity bands.
BMR calculator
BMR is the energy your body uses at complete rest. This calculator runs the Mifflin-St Jeor equation, the 1984 revision of Harris-Benedict, and Katch-McArdle when you have a lean-mass figure, then shows the gap between them, because that gap is bigger than most calculators admit.
Maintenance calorie calculator
Maintenance calories are the same quantity as TDEE, under a different name: the energy that leaves your weight where it is. This calculator estimates it from the Mifflin-St Jeor equation and an activity factor, shows the range that estimate really covers, and explains why the scale is the only real check.
Calorie deficit calculator
A calorie deficit is the gap between the energy you use and the energy you eat. This calculator works out that gap from your estimated maintenance figure, converts it using the 3,500 kcal per pound rule, and shows the correction Hall published in 2008 for why that rule overstates things.
Weight loss calculator
This projects weight change from a daily calorie deficit as a range, not a single figure and not a date. The high end is the straight-line 3,500 kcal per pound arithmetic; the low end applies the 2011 finding by Hall and colleagues that about half of an eventual change arrives in the first year.
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. Every preset sits inside the Acceptable Macronutrient Distribution Range the IOM published, and any custom split is checked against those percentages rather than scored.
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. This shows each of them in grams for your weight.
Water intake calculator
The eight-glasses rule is about 1.9 litres of drinking water and nobody published it. The IOM set an Adequate Intake for total water of 3.7 litres a day for men and 2.7 for women, food included, and this calculator shows that figure beside the two conventions people quote instead.
Max heart rate calculator
A maximum heart rate calculator estimates the fastest your heart beats at all-out effort. This one runs three published equations at once: Fox 220 minus age, Tanaka 208 minus 0.7 times age, and Gulati 206 minus 0.88 times age for women. It shows the gap between them and states that 220 minus age was never a validated regression.
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. Enter a resting heart rate and it also computes Karvonen zones from heart rate reserve, which sit higher, and prints the intensity classification ACSM actually published beside the five zone convention.
Lean body mass calculator
A lean body mass calculator estimates how much of your weight is not fat, from your height, weight and sex. It runs the Boer, James and Hume equations together rather than picking one, because at 80 kilograms and 180 centimetres they land 4.93 kilograms apart, and that spread is the honest answer.
Body fat calculator
A body fat calculator estimates what share of your weight is fat. This one runs the Hodgdon and Beckett tape method from your neck, waist and hip measurements and the Deurenberg BMI equation, shows each with the error band its own paper reports, and adds your waist to height ratio with the NICE bands.
One rep max calculator
A one rep max calculator predicts the heaviest single you could lift from a set you actually completed. It runs Epley and Brzycki together, shows where they agree and where they diverge, gives the percentage table for every rep count, and widens the stated uncertainty above ten reps where the published validation stops.
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. It also projects equivalent times at 5K, 10K, half marathon and marathon using the Riegel equation, shown as a spread rather than a promise.
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. Every MET value comes from the 2024 Adult Compendium with its activity code, and the tool shows the net figure alongside the gross one.
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. It also shows how much of the fast falls while you are asleep. It is clock arithmetic, and it does not recommend a schedule or predict a result.
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. It reports a range, never one number, and shows every figure with the paper it came from. The addition is ours; none of those studies did it.
My 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. Everything stays in this browser: there is no account, nothing is uploaded, and you can export or delete it all whenever you like.
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. It orders a list for you; it does not assess your health or recommend anything.
Turn these targets into meals with the kitchen-math tools at recipesandmeasures.com
For sleep timing — bedtime, sleep cycles, naps, caffeine cutoff — see theballastprinciple.com
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