BMR calculator: basal metabolic rate from three equations
Estimated basal metabolic rate for 80 kg, 180 cm, 30 yearsworked example
1,780 kcal
- Harris-Benedict, revised 1984
- 1,854 kcal+74 kcal against Mifflin-St Jeor
- Spread across the equations shown
- 74 kcal/dayAll three are published, peer-reviewed and disagree
Mifflin-St Jeor is the figure shown large because a 2005 systematic review found it landed within 10% of a measured value more often than the alternatives. The other rows are here so the 74 kcal of disagreement between published equations is visible rather than hidden by whichever one a calculator happens to use.
Realistic range
1,602 kcal to 1,958 kcal
The ±10% band the Frankenfield 2005 review used as its accuracy criterion, applied to the Mifflin-St Jeor figure. A measured resting metabolic rate from indirect calorimetry is the only way to narrow it.
| Equation | Result | Reported error | What it uses |
|---|---|---|---|
| Mifflin-St Jeor (1990) | 1,780 kcal | ±10% | Weight, height, age, sex |
| Harris-Benedict, revised 1984 | 1,854 kcal | ±14% | Weight, height, age, sex |
Resting energy is only part of a day. To get the figure that matters for eating, multiply it by an activity factor on the TDEE calculator — where the multiplier is labelled the convention it is.
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.
- Resting energy expenditure (Mifflin-St Jeor) — BMR (kcal/day) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(y) + 5 (male) or - 161 (female). Verified against Mifflin et al., Am J Clin Nutr 1990 (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.)
- Harris-Benedict, revised (Roza and Shizgal) — 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). Verified against Roza and Shizgal, Am J Clin Nutr 1984 (The paper reports these equations estimate one person's resting energy expenditure to a precision of about 14%.)
- Resting metabolic rate from fat-free mass (Katch-McArdle / Cunningham) — RMR (kcal/day) = 370 + 21.6 x fat-free mass (kg). Verified against Cunningham, Am J Clin Nutr 1991 (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.)
- Accuracy of resting-metabolic-rate equations — the review's accuracy criterion was a prediction within 10% of measured RMR. Verified against Frankenfield et al., J Am Diet Assoc 2005 (systematic review) (This describes how often an equation lands within 10% across groups of people. It is not a confidence interval for one person's result.)
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Frequently asked questions
What is the difference between BMR and RMR?
Which BMR equation is the most accurate?
When is the Katch-McArdle equation worth using?
Why is the Harris-Benedict number higher than the others?
Can I raise my BMR?
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