BMR Calculator Free Online
Calculate Basal Metabolic Rate (BMR) — the calories your body burns at complete rest — using the modern Mifflin-St Jeor equation. Includes TDEE for 5 activity levels.
Results
Pro — bulk batch calculation, API access, history & favorites
API access · Priority queue · Team workspace
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BMR Calculator Features
Mifflin-St Jeor
The most accurate BMR formula for the general population (validated 2005). More reliable than older Harris-Benedict (1919) which overestimates BMR by ~5%.
5 Activity Levels
Sedentary (1.2x BMR) through Extra Active (1.9x BMR). Be honest — most people overestimate. "Moderately active" requires 30+ min strenuous exercise 3-5 days/wk.
Calorie Targets
TDEE − 500 kcal/day = ~0.5 kg/week loss. TDEE + 500 = ~0.5 kg/week gain. (1 kg fat ≈ 7,700 kcal — stricter rule of thumb than the old "3500 kcal/lb".)
Live Calculation
All values update as you type. Switch metric ↔ imperial freely.
Metric & Imperial
Heights in cm or inches, weights in kg or pounds. Same equation under the hood.
100% Private
All math runs in your browser. No data leaves your device.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Full bmr calculation | ||
| Live calculation | ||
| All-units result panel | ||
| Bulk batch calculation | — | |
| REST API access | — | |
| Save & share calculations | — |
Frequently Asked Questions
Basal Metabolic Rate — the calories your body burns at complete rest just to keep organs functioning, breathe, and maintain body temperature. Typically 60-75% of total daily calories.
Total Daily Energy Expenditure = BMR × activity multiplier. Includes calories burned through all daily movement, exercise, and the thermic effect of food.
Male: 10×kg + 6.25×cm − 5×age + 5. Female: 10×kg + 6.25×cm − 5×age − 161. Result in kcal/day. Published 1990, validated 2005, considered most accurate for general population.
Eat at TDEE to maintain weight. Eat below TDEE (but ideally not below BMR) to lose. Eating below BMR long-term slows metabolism and risks nutrient deficiencies.
Mifflin-St Jeor is accurate within ±10% for most adults. Less accurate for very lean (athletes), very obese, or elderly people. For precise measurements, use indirect calorimetry.