TDEE calculator (Mifflin-St Jeor)

TDEE — your real daily calorie burn

Total Daily Energy Expenditure (TDEE) = BMR × activity factor. It's the number that decides whether you lose, hold, or gain weight on a given diet.

The formula stack

1. BMR (basal metabolic rate) — calories to keep you alive at rest. We use Mifflin-St Jeor, the most accurate of the common BMR estimators per direct calorimetry studies.
2. Activity factor — multiplier for everything above resting (1.2 sedentary → 1.9 extreme).
3. Goal adjustment — cut at TDEE × 0.8 (20% deficit), build at TDEE × 1.1 (10% surplus).

Why 20% cut and 10% build (not symmetric)

A 20% deficit produces ~1-2 lb/wk fat loss for most people — sustainable, preserves muscle if protein is high. Larger deficits compromise muscle and adherence.

For building, a 10% surplus is genuinely enough. You can't build muscle faster than ~0.5 lb/wk (advanced) to 1.5 lb/wk (newbie). A bigger surplus just adds fat, not muscle. The "dirty bulk" tradition is mostly an excuse to eat ice cream.

Real-world calibration

This calc is an estimate within ±10-15%. Track for two weeks at the calculated maintain number. If your weight is stable, the number is right. If it's drifting, adjust ±100-200 calories and retry. The math gives you the starting point — the scale gives you the truth.