Understanding This Calculator
Basal Metabolic Rate is the number of calories your body needs to maintain vital functions — breathing, circulation, cell production — while completely at rest. It typically accounts for 60-75% of total daily calorie burn, making it the foundation for any calorie or weight-management plan.
This calculator uses the Mifflin-St Jeor equation, published in 1990 and validated as more accurate than the older Harris-Benedict formula across most modern populations.
- w weight in kilograms
- h height in centimeters
- a age in years
| Formula | Year | Notes |
|---|---|---|
| Mifflin-St Jeor | 1990 | Most accurate for modern populations (used here) |
| Harris-Benedict | 1919 (rev. 1984) | Older, tends to overestimate by 5% |
| Katch-McArdle | — | Uses lean body mass; needs body-fat % input |
Frequently Asked Questions
Is BMR the same as the calories I should eat?
No — BMR is calories at complete rest. Your Total Daily Energy Expenditure (TDEE), which factors in activity, is what you should use for calorie targets. See our TDEE Calculator.
Why does BMR decrease with age?
Muscle mass naturally declines with age, and muscle is metabolically more active than fat, so BMR tends to drop roughly 1-2% per decade after age 20.