BMR Calculator
Your Basal Metabolic Rate — the calories your body burns at complete rest — compared across the three leading formulas.
What is BMR?
Your Basal Metabolic Rate is the energy your body spends just keeping you alive — heartbeat, breathing, brain activity, cell repair — measured at complete rest. For most people it is 60-70% of all calories burned in a day. Movement, exercise and digesting food make up the rest.
Three formulas, one goal
Mifflin-St Jeor (women): 10×kg + 6.25×cm − 5×age − 161
Harris-Benedict (men): 13.397×kg + 4.799×cm − 5.677×age + 88.362
Harris-Benedict (women): 9.247×kg + 3.098×cm − 4.330×age + 447.593
Katch-McArdle: 370 + 21.6 × lean body mass (kg)
- Mifflin-St Jeor (1990) — the American Dietetic Association's pick for accuracy in the general population. Our default.
- Harris-Benedict (1919, revised 1984) — the classic; tends to read slightly high.
- Katch-McArdle — computes from lean mass, so it shines for lean, muscular people who know their body fat percentage.
Can you raise your BMR?
Modestly, yes. Muscle tissue burns more at rest than fat, so resistance training plus adequate protein nudges BMR upward over months. Crash dieting does the opposite — severe restriction can suppress resting metabolism, one reason gradual deficits work better long-term.
Frequently asked questions
What is a normal BMR?
Most adult men land between 1,500 and 2,000 kcal/day, most women between 1,200 and 1,600 kcal/day. Bigger, younger and more muscular bodies run higher.
BMR vs TDEE — what is the difference?
BMR is what you burn at total rest. TDEE adds daily movement, exercise and digestion. You should never eat below BMR for extended periods without medical supervision; calorie targets are set from TDEE.
Which BMR formula is most accurate?
Research comparisons consistently favor Mifflin-St Jeor for the general population. If you know your body fat percentage reliably, Katch-McArdle can be more precise for athletic body types.
Does metabolism really slow with age?
Later and less than most people think. Large 2021 pooled data (Science, Pontzer et al.) shows metabolism is fairly stable from age 20 to 60 once body size is accounted for — much of "age-related" slowdown is actually lost muscle and activity.
References
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr, 1990.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr, 1984.
- Pontzer H, et al. Daily energy expenditure through the human life course. Science, 2021.