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Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation. Get personalized calorie recommendations.
Calculate your daily calorie needs
💡BMR uses the Mifflin-St Jeor equation, the most accurate formula for modern populations according to the American Dietetic Association.
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Reviewed by CalculatorApp.me Health Editorial Team · Updated March 2026 · 10 min read
Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions at complete rest — breathing, circulation, cell production, and organ function. It represents the minimum energy required to keep you alive.
BMR accounts for 60–75% of your total daily energy expenditure (TDEE), making it the single largest contributor to your caloric needs. Understanding your BMR is the foundation of any effective nutrition and weight management plan.
Your BMR is influenced by age, sex, height, weight, and lean body mass. Muscle tissue is metabolically active — people with more muscle burn more calories at rest.
Validated in multiple large studies. Considered the most accurate for most adults and is recommended by the Academy of Nutrition and Dietetics.
The original 1919 equation revised in 1984 by Roza and Shizgal. Widely used for over a century.
Uses lean body mass instead of total weight. More accurate for athletes and bodybuilders with significant muscle mass.
Your Total Daily Energy Expenditure (TDEE) is BMR multiplied by an activity factor representing your lifestyle. TDEE is the actual number of calories you need to maintain your current weight.
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | × 1.2 |
| Lightly Active | Light exercise 1–3 days/week | × 1.375 |
| Moderately Active | Moderate exercise 3–5 days/week | × 1.55 |
| Very Active | Hard exercise 6–7 days/week | × 1.725 |
| Extremely Active | Very hard exercise + physical job | × 1.9 |
TDEE = BMR × Activity Multiplier. Most people overestimate their activity level — when in doubt, choose a lower category.
French chemist Antoine Lavoisier discovers that animals produce heat by oxidizing food, laying the groundwork for metabolism science.
James Arthur Harris and Francis Gano Benedict publish the first widely-used BMR formula based on 239 subjects at the Carnegie Institution of Washington.
Roza and Shizgal revise the original formula based on a larger population, correcting systematic overestimation biases in the 1919 version.
M.D. Mifflin and colleagues publish their equation based on 498 subjects, which proves more accurate than Harris-Benedict for contemporary populations due to changes in average body composition.
A lean-mass-based formula is developed that accounts for individual differences in body composition, proving superior for athletic populations.
Large-scale studies validate Mifflin-St Jeor as the most accurate single formula for free-living adults, now the standard recommendation by the Academy of Nutrition and Dietetics.
Once you know your TDEE (BMR × activity level), you can set calorie targets for your goal and then distribute those calories across macronutrients.
Preserves muscle during calorie deficit. Higher end (1.0g) for active individuals and those over 40.
Primary energy source. Higher for endurance athletes; lower for sedentary individuals or low-carb approaches.
Essential for hormone production, fat-soluble vitamin absorption, and brain function. Never go below 0.3g/lb.
| Term | Definition | Includes Activity? | Used For |
|---|---|---|---|
| BMR | Calories burned completely at rest (awake, fasted) | No | Research baseline |
| RMR | Resting Metabolic Rate — slightly lower conditions than BMR | No | Clinical measurements |
| TDEE | Total Daily Energy Expenditure including all activity | Yes | Setting calorie goals |
Mifflin et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals.
Academy of Nutrition and Dietetics recommends Mifflin-St Jeor as the preferred BMR estimator.
Research on resting energy expenditure differences across metabolic phenotypes and body compositions.
BMR is the same as calories to eat
BMR is the minimum needed at complete rest. You should eat at TDEE (BMR × activity) to maintain weight, not at raw BMR.
Eating more increases your metabolism
While thermic effect of food exists (~10% of calories), overeating does not significantly boost BMR. Resistance training is what meaningfully raises BMR.
Low-calorie diets boost metabolism
Severe calorie restriction suppresses BMR through metabolic adaptation — known as "starvation mode." The body becomes more efficient at lower intakes.
BMR stays constant throughout life
BMR declines ~1–2% per decade after age 20, primarily due to loss of muscle mass. Regular strength training can substantially offset this decline.
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