BMR Calculator

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest just to keep you alive — breathing, circulation, cell repair, organ function — over 24 hours. It is the floor of your energy needs, before any movement or digestion is added. It tells you roughly how much energy your body uses even on a day you do nothing, the starting point for any calorie target.

This tool uses the Mifflin-St Jeor equation (1990), the most validated for general-population use. Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: the same but − 161 instead of + 5. It is an estimate from your body size, age, and sex — a well-grounded starting point, not a direct measurement of your metabolism.

BMR is what you burn at rest. TDEE — total daily energy expenditure — is BMR plus everything else: digestion, day-to-day movement, and exercise. TDEE is the number that matters for weight goals because it reflects your real daily burn. Feed your BMR into the TDEE Calculator to get there.

BMR is effectively the floor for how little you should eat. Dropping far below it for long periods deprives essential functions and tends to backfire — the body defends itself by lowering expenditure. For fat loss, use a modest deficit against your TDEE (not below your BMR); for gaining, a modest surplus. Knowing your BMR keeps the deficit from becoming counterproductive.

Muscle mass is the biggest lever you control — more lean tissue raises resting burn, which is why resistance training helps. BMR also declines gradually with age and differs by body size and sex. Prolonged aggressive dieting can lower it through adaptive thermogenesis, as the body downshifts to conserve energy — which is why crash diets stall and why preserving muscle with adequate protein and strength training matters during a deficit.