Mifflin-St Jeor BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + s, where s is +5 for males and −161 for females. The BMR is multiplied by an activity factor from 1.2 (sedentary) to 1.9 (very active). When you enter a body-fat percentage, Katch-McArdle BMR = 370 + 21.6·lean body mass(kg) is used instead.
Mifflin MD, St Jeor ST, et al. (1990) American Journal of Clinical Nutrition; Katch & McArdle (1996).
±10–15% for most adults. Activity multipliers are population averages, so the single largest source of error is over-estimating your activity level. Verify against 2–3 weeks of real intake and weight data.
People under 18, pregnant or breastfeeding women, and those with metabolic or endocrine conditions that alter energy expenditure. In those cases, rely on clinical assessment.
Frequently asked questions
TDEE is your Total Daily Energy Expenditure — the total calories you burn in a day, including your resting metabolism, digestion, daily movement, and exercise. Eat that many calories and your weight stays stable.
We estimate your BMR with the Mifflin-St Jeor equation, then multiply by an activity factor from 1.2 (sedentary) to 1.9 (very active). If you enter a body-fat percentage, we switch to the Katch-McArdle equation, which is more accurate for lean or muscular people.
No equation is exact. Different validated formulas disagree by 5–15%, and activity multipliers are population averages. The range reflects that honest uncertainty — treat the midpoint as a starting estimate, not a precise target.
For most people it lands within about 10–15% of true expenditure. The only way to know your real number is to track your intake and weight for 2–3 weeks and adjust — which is exactly what the self-calibration protocol on this page walks you through.
No — to lose weight you eat below your TDEE. A deficit of 15–25% is a sustainable starting point. This calculator never suggests eating below your BMR, and caps the deficit at 25% to protect muscle and hormones.
Recalculate whenever your weight changes by more than about 5 kg (10 lb), your activity level shifts, or your progress stalls for 2–3 weeks. Your TDEE falls as you lose weight, so periodic updates keep your targets realistic.
Yes. The activity multiplier is meant to cover your typical weekly exercise. If you separately log workout calories, choose a lower activity level (like sedentary or light) to avoid counting exercise twice.