What this calculator gives you
Two numbers, side by side:
- BMR — calories your body burns at complete rest in 24 hours. This is the floor.
- TDEE — BMR × activity multiplier. This is the actual number of calories you burn on a typical day. Use TDEE for any calorie target.
The strip on the right shows TDEE at all five standard activity levels (sedentary → extra active). Click any row to set it as your “selected” level — useful for comparing what changing your activity does to your daily calorie budget.
Which formula to use
- Mifflin-St Jeor (default) — the Academy of Nutrition and Dietetics’ recommendation for adults. Most accurate population-level formula since 1990.
- Harris-Benedict (revised 1984) — still widely cited, but typically overestimates by ~5% for the modern population. Useful if you want to compare against an older app or textbook.
- Katch-McArdle — the most accurate of the three if you have a real body-fat measurement. Uses lean body mass directly, so it’s independent of sex (LBM does the work).
If you pick Katch-McArdle but don’t enter a body-fat percentage, the tool falls back to Mifflin and tells you why.
Privacy
The math runs entirely in your browser via the pure calculateBMR function. Editing any field produces zero network requests — you can verify this in the Network tab. The page doesn’t store inputs in localStorage, doesn’t include them in analytics, and never transmits anything about your body.