BMR calculator
Calculate basal metabolic rate with Mifflin–St Jeor, compared with revised Harris–Benedict, with every number shown.
The formula
Example: 35-year-old man, 5′10″ (177.8 cm), 180 lb (81.6 kg) → 1,758 kcal BMR; moderately active (×1.55) TDEE 2,725 kcal.
Setting a target
A 500 kcal daily deficit is the common rule of thumb for about 1 lb (0.45 kg) per week. Lifting weights and eating around 1.6 g/kg protein helps protect lean mass (the general adult RDA is 0.8 g/kg).
FAQ
What is BMR?
Basal metabolic rate is the energy your body uses at complete rest for breathing, circulation and temperature — typically 60–70% of daily burn.
Mifflin–St Jeor vs Harris–Benedict?
Both use height, weight, age and sex, but a 2005 systematic review (Frankenfield et al.) found Mifflin–St Jeor more accurate for healthy adults. Revised Harris–Benedict (Roza & Shizgal 1984) is shown for comparison.
Does BMR drop with age?
The formula subtracts 5 kcal per year of age. In practice most of the drop comes from losing muscle, which strength training can slow.
Should I eat only my BMR?
No. Your real daily burn is TDEE (BMR × activity). Set diet targets from TDEE; eating far below BMR is not recommended.
Is it accurate for muscular people?
The equation does not use body-fat %, so very muscular or very lean/heavy people can see larger errors. Allow about ±10%.
Sources
- Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr 1990;51(2):241–247. doi:10.1093/ajcn/51.2.241
- Frankenfield D, et al. Systematic review of RMR prediction equations — Mifflin–St Jeor most accurate. J Am Diet Assoc 2005;105(5):775–789. doi:10.1016/j.jada.2005.02.005
- Roza AM, Shizgal HM. Revised Harris–Benedict. Am J Clin Nutr 1984;40(1):168–182. doi:10.1093/ajcn/40.1.168
- Protein 1.6 g/kg (resistance-training adults): Morton RW, et al. "A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults." British Journal of Sports Medicine (Br J Sports Med) 2018;52(6):376–384. doi:10.1136/bjsports-2017-097608
- Activity multipliers (1.2–1.9) are conventional estimates; individual variation is large.
Formulas and sources checked 2026-10-16. Not medical advice. Pregnant, nursing, under 18 or with a medical condition — ask a professional.