SnapMyGym
Find your total daily energy expenditure and cut/bulk calorie targets from BMR and activity level. Free TDEE calculator, no signup.
TDEE — total daily energy expenditure — is how many calories you burn per day including training and daily movement. It's your maintenance line: eat under it and you lose weight, over it and you gain. Every cut and every bulk starts from this number.
The calculator estimates your basal metabolic rate with the Mifflin-St Jeor equation, then multiplies by an activity factor from 1.2 (sedentary) to about 1.9 (very active). That multiplier is the biggest source of error — most people overestimate their activity level by half a tier.
Treat the output as a two-week hypothesis. Eat the number, weigh daily, average weekly: if the weekly average holds steady, that is your real TDEE; if it drifts, adjust by 100–200 calories and re-test. A month of your own data beats any equation.
Typically within ±10%, which is a couple hundred calories for most adults. That's why you verify against two weeks of scale-weight data instead of trusting the estimate — your weight trend is a personal measurement, while the equation is a population average.
300–500 calories below TDEE loses roughly 0.5–1 lb per week while preserving muscle and training quality. Bigger deficits work briefly but cost strength, adherence, and muscle the longer they run.
Nearly always because the deficit isn't real: intake is underestimated (cooking oils, sauces, untracked bites), daily activity has quietly dropped, or water retention is masking fat loss. Give any change three weeks of weekly averages before concluding it failed.
Want the number to actually go up? Snap My Gym builds percentage-based programs around your lifts and tracks them automatically. More evidence-first training articles on the blog.