Calorie Needs Calculator
BMR and TDEE by the Mifflin-St Jeor equation — the formula dietitians actually use — plus sensible targets for each goal.
Calculate your daily calories
BMR, TDEE, and the formula behind the numbers
Your BMR (basal metabolic rate) is what your body burns at complete rest — keeping you warm, breathing, thinking. Your TDEE (total daily energy expenditure) multiplies that by an activity factor to cover real life. This calculator uses the Mifflin-St Jeor equation, which research has found the most accurate of the common formulas:
A worked example
A 40-year-old man, 5'10", 180 lb, lightly active: BMR comes to about 1,755 calories, TDEE about 2,415. To lose roughly a pound per week he'd target ~1,915 (a 500-calorie deficit, since a pound of fat is ~3,500 calories); to gain lean mass slowly, ~2,665. These are starting points — the real test is what your scale does over 3–4 weeks, after which you adjust by 100–200 calories.
The mistakes that break calorie math
Three classics: overstating activity (a desk job plus three gym visits is "light," not "very active" — the gym hour doesn't cancel the other 23), under-tracking intake (oils, sauces, and bites add up to hundreds of invisible calories), and crash deficits — cutting far below BMR loses muscle, tanks energy, and rebounds. A moderate deficit you can sustain for months beats an aggressive one you abandon in two weeks, every single time.
Frequently asked questions
Why do different calculators give different numbers?
Different formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and rounding. They're all estimates within ~10%; your real-world weight trend over a few weeks is the ground truth that calibrates the number.
Should I eat below my BMR to lose faster?
Generally no. Aggressive deficits below BMR tend to cost muscle, energy, and adherence. A 500-calorie deficit from TDEE — roughly a pound a week — is the sustainable standard.
Do I need to eat back exercise calories?
If you chose an activity level that already includes your exercise, no — they're baked in. Counting them twice (in the multiplier AND eating them back) is one of the most common stalls.
How accurate are these numbers?
Within about 10% for most people; metabolism varies with genetics, muscle mass, and hormones. Use the result as a 3-week experiment: track honestly, weigh consistently, and adjust based on what actually happens. For medical conditions, work with a doctor or registered dietitian.