BMR & TDEE calculator guide
How the BMR and TDEE calculator works, which of the three formulas to pick, and how to turn the number into a diet.
1 min read
Written & reviewed by Ricardo Tapia·Last updated
Your BMR (basal metabolic rate) is the energy your body burns at complete rest. Your TDEE (total daily energy expenditure) is BMR multiplied by an activity factor — the calories you actually burn in a day, and the starting point for any diet.
TDEE = BMR × activity multiplier (1.2 sedentary → 1.9 very active).
Three formulas — which to pick?
- Mifflin–St Jeor (1990) — derived from a modern population; today's most accurate estimate for the general public. Use this if you're unsure.
- Harris–Benedict — the classic equation first published by J. A. Harris & F. Benedict in 1919, revised by Roza & Shizgal in 1984. Still widely used; tends to slightly overestimate for people with higher body fat. Great for cross-checking.
- Katch–McArdle — uses your lean body mass (needs your body-fat %), so it accounts for muscle. The best choice if you're lean/muscular and know your body fat.
All three estimate the same thing. If two formulas disagree by a few hundred kcal, that's normal — pick one, track your weight for 2 weeks, and adjust from reality.
Try it
Run your own numbers in the TDEE calculator, then feed the result into the macro calculator to split it into protein, carbs and fat.
Sources & references
- 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.
- Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci. 1918;4(12):370-373.
Educational content only. Not medical advice — consult a professional for your situation.