BMR Formula Comparison
Six published equations, the same person, a 300-calorie spread. This page shows every major BMR formula in full, runs them all on identical inputs so you can see how far apart they land, and explains which one to trust for which body.
The equations
All six predict basal or resting metabolic rate in kilocalories per day. Weight is in kilograms, height in centimetres, age in years, and lean body mass (LBM) in kilograms.
| Equation | Formula | Needs |
|---|---|---|
| Mifflin-St Jeor 1990 |
Men: 10W + 6.25H − 5A + 5 Women: 10W + 6.25H − 5A − 161 |
Weight, height, age, sex |
| Harris-Benedict (revised) Roza & Shizgal, 1984 |
Men: 88.362 + 13.397W + 4.799H − 5.677A Women: 447.593 + 9.247W + 3.098H − 4.330A |
Weight, height, age, sex |
| Katch-McArdle 1996 |
370 + 21.6 × LBM | Lean body mass |
| Cunningham 1980 |
500 + 22 × LBM | Lean body mass |
| Owen 1986/1987 |
Men: 879 + 10.2W Women: 795 + 7.18W |
Weight, sex |
| Schofield (WHO/FAO) 1985, ages 30–60 |
Men: 11.472W + 873.1 Women: 8.126W + 845.6 |
Weight, sex, age band |
The same two people, six ways
Below, every equation is run on identical inputs. The lean-mass equations need a body fat estimate, so we have assumed 15 percent for the man and 25 percent for the woman.
Man, 30 years, 80 kg, 180 cm, 15% body fat (68 kg LBM)
| Equation | BMR | vs Mifflin | TDEE at 1.55× |
|---|---|---|---|
| Owen | 1,695 | −85 | 2,627 |
| Mifflin-St Jeor | 1,780 | — | 2,759 |
| Schofield | 1,791 | +11 | 2,776 |
| Katch-McArdle | 1,839 | +59 | 2,850 |
| Harris-Benedict | 1,854 | +74 | 2,874 |
| Cunningham | 1,996 | +216 | 3,094 |
Woman, 30 years, 65 kg, 165 cm, 25% body fat (48.8 kg LBM)
| Equation | BMR | vs Mifflin | TDEE at 1.55× |
|---|---|---|---|
| Owen | 1,262 | −108 | 1,956 |
| Mifflin-St Jeor | 1,370 | — | 2,124 |
| Schofield | 1,374 | +4 | 2,130 |
| Katch-McArdle | 1,423 | +53 | 2,206 |
| Harris-Benedict | 1,430 | +60 | 2,217 |
| Cunningham | 1,573 | +203 | 2,438 |
The spread between the lowest and highest estimate is about 300 calories in both cases — 17 percent for the man, 23 percent for the woman. Multiply by an activity factor and the gap widens to nearly 500 calories a day. That is the difference between a moderate deficit and maintenance, from nothing but a choice of equation, which is exactly why “which calculator is right” is a question worth taking seriously.
Which one should you use?
| If you are… | Use | Why |
|---|---|---|
| An average adult with no body fat measurement | Mifflin-St Jeor | The best-validated general-population equation; the default on this site |
| Lean and muscular, with a reliable body fat figure | Katch-McArdle | Scales with lean mass, so it does not penalise you for being heavy with muscle |
| A competitive athlete with a DEXA scan | Cunningham | Derived from athletic populations; runs highest, which suits high-training-volume bodies |
| Living with obesity | Mifflin-St Jeor | Validated across obese and non-obese groups; Harris-Benedict overestimates here |
| Curious about the historical number | Harris-Benedict | The 1919 original, revised in 1984; still the most cited, and reliably a little high |
A 2005 review in the Journal of the American Dietetic Association compared the major predictive equations against measured resting metabolic rate and found Mifflin-St Jeor the most reliable for non-obese and obese adults alike, predicting within 10 percent of measured RMR more often than the alternatives. That is the reason it is the default in our BMR calculator and TDEE calculator.
What “within 10 percent” actually means
Accuracy claims for these equations are usually stated as the proportion of people whose measured rate falls within 10 percent of the prediction. For Mifflin-St Jeor that proportion is roughly 70 percent — which also means about three in ten people are off by more than 10 percent, and a smaller group by considerably more. On a 1,800-calorie BMR, being 10 percent out is 180 calories; carried through an activity multiplier, nearer 280.
None of that makes the equations useless. It makes them a starting point. Pick one, eat at the number it gives for two to three weeks, weigh yourself consistently, and let the trend correct the estimate. Your own data beats every equation on this page after about a fortnight — the formula’s only job is to stop you starting from zero.
Sources
- Mifflin MD, St Jeor ST et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition.
- Frankenfield D, Roth-Yousey L, Compher C (2005). Comparison of predictive equations for resting metabolic rate in healthy non-obese and obese adults. Journal of the American Dietetic Association.
- Roza AM, Shizgal HM (1984). The Harris-Benedict equation reevaluated. American Journal of Clinical Nutrition.
- Cunningham JJ (1980). A reanalysis of the factors influencing basal metabolic rate in normal adults. American Journal of Clinical Nutrition.
- Owen OE et al. (1986, 1987). A reappraisal of the caloric requirements of healthy women and men. American Journal of Clinical Nutrition.
- Schofield WN (1985). Predicting basal metabolic rate: new standards and review of previous work. Human Nutrition: Clinical Nutrition.
Last reviewed: September 2026.
Last updated September 14, 2026.