Calorie Calculator

It computes your BMR with the Mifflin-St Jeor equation from age, sex, height, and weight, multiplies that by an activity factor (1.2 for sedentary up to 1.9 for extra active) to get TDEE, and — if you've chosen weight loss or muscle gain — adjusts from there using 7,700 kcal per kilogram of body fat, divided across 7 days, for the deficit or surplus.

A systematic review by Frankenfield and colleagues found it predicts measured resting energy expenditure more accurately than the older 1919 Harris-Benedict equation, particularly in people with overweight or obesity — which is why the Academy of Nutrition and Dietetics recommends it as the default for both non-obese and obese adults.

The calculator won't display a target below 1,200 kcal/day for women or 1,500 kcal/day for men, even if your chosen deficit would otherwise push it lower. Sustained intake below those levels is generally recommended only under medical supervision, so the number is raised to the floor and the reason is shown rather than the target silently dropping.

Treat it as a starting point, not a fact about your body — predictive equations like Mifflin-St Jeor typically agree with measured resting energy expenditure within about 10-15%, and individual metabolism varies with genetics, muscle mass, and other factors the formula can't see. The practical approach is to use the number as a baseline and adjust it against your own weight trend over a few weeks.

Yes — TDEE falls as body weight falls, since a lighter body burns less both at rest and in motion. A target calculated at your starting weight will overshoot maintenance once you've lost a meaningful amount, so recalculating periodically keeps the deficit or surplus honest rather than shrinking without you noticing.