BMR Calculator

Mifflin-St Jeor: BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + s, where s is +5 for males and −161 for females. Harris-Benedict and, when body fat % is given, Katch-McArdle (370 + 21.6·lean mass) are shown for comparison.

Mifflin MD, St Jeor ST, et al. (1990) American Journal of Clinical Nutrition; Roza & Shizgal (1984); Katch & McArdle (1996).

±10% for most adults, wider at the extremes of age or body composition. Katch-McArdle is more accurate for very lean or muscular people because it uses lean mass directly.

People under 18, pregnant or breastfeeding women, and those with thyroid or other metabolic conditions that alter resting energy use.

Basal Metabolic Rate is the number of calories your body burns at complete rest to keep vital functions running — breathing, circulation, cell repair, and brain activity. It's the single largest part of your daily calorie burn.

BMR is your at-rest burn. TDEE (Total Daily Energy Expenditure) is BMR plus everything else — digestion, daily movement, and exercise. TDEE is always higher, and it's the number you use to set calorie goals.

For most people the Mifflin-St Jeor equation is the most accurate of the classic formulas, which is why it's our primary result. If you know your body-fat percentage, Katch-McArdle is more accurate because it's based on lean mass.

Each was derived from a different population and uses different coefficients. Harris-Benedict (1918, revised 1984) tends to run slightly high for modern bodies. The spread between them is a useful reminder that any BMR figure is an estimate, not an exact measurement.

No. Eating at or below your BMR for long periods isn't recommended — it's the floor your body needs at rest. To lose weight, subtract a moderate deficit from your TDEE, not your BMR.

Yes. BMR falls as you lose weight or age, and rises with more lean muscle mass. Recalculate when your weight changes noticeably, and consider strength training to preserve muscle and keep your metabolism higher.