BMR Calculator — Basal Metabolic Rate
Calculate your Basal Metabolic Rate — the calories your body burns at complete rest — using the Mifflin-St Jeor and Harris-Benedict equations.
Understanding Your Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate is the number of calories your body burns each day just to keep you alive — breathing, circulating blood, regulating body temperature, and maintaining organ function — with zero physical activity. BMR accounts for 60–75% of total daily calorie expenditure in sedentary individuals, making it the most important component of your overall energy needs.
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161
Mifflin-St Jeor vs. Harris-Benedict
The Mifflin-St Jeor equation (1990) is considered more accurate for modern populations and is preferred by most registered dietitians. The older Harris-Benedict equation (1919, revised 1984) tends to overestimate BMR by roughly 5% in most populations. Both are included for comparison.
| Formula | Published | Accuracy |
|---|---|---|
| Mifflin-St Jeor | 1990 | ±10% for most adults (preferred) |
| Harris-Benedict (revised) | 1984 | ±15%, tends to overestimate |
| Katch-McArdle | 1975 | Most accurate if body fat % is known |
Factors That Affect Your BMR
- Age: BMR decreases approximately 1–2% per decade after age 30, primarily due to declining muscle mass
- Sex: Men typically have a 5–10% higher BMR than women of the same size due to greater muscle mass and lower body fat percentage
- Body composition: Muscle tissue burns ~3× more calories at rest than fat tissue — increasing lean mass raises BMR
- Thyroid function: Hyperthyroidism significantly raises BMR; hypothyroidism lowers it
- Temperature: BMR increases in cold environments as the body works to maintain core temperature
How to Use Your BMR
BMR alone isn't useful for most practical purposes — it represents zero activity. To find your maintenance calories, multiply your BMR by an activity factor to calculate your TDEE (Total Daily Energy Expenditure). Use our TDEE Calculator to do this automatically, then visit our Calorie Calculator to set a target for weight loss or gain.