BMR calculator

About this calculation

Basal Metabolic Rate (BMR) is the number of calories your body uses each day to keep essential functions running at complete rest: breathing, circulating blood, regulating temperature, maintaining and repairing cells. It is the floor of your daily energy needs. Any movement, digestion, or exercise sits on top of it.

The Mifflin-St Jeor equation

Published in 1990 by Mifflin, St Jeor, and colleagues, this equation was derived from indirect calorimetry on nearly 500 adults and has outperformed older equations (Harris-Benedict, Owen) in validation studies across diverse populations. It is the default BMR equation used in most clinical and sports-nutrition contexts today.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

BMR vs TDEE

BMR is calories at complete rest. Total Daily Energy Expenditure (TDEE) is BMR multiplied by an activity factor — typically 1.2 for sedentary up to 1.9 for very active. TDEE is what you actually burn on a typical day; BMR is the underlying baseline. The panel above shows the same BMR at each activity factor so you can see the range.

For a full TDEE calculation with activity level selection and weight-change targets, see the TDEE calculator. For splitting those calories into protein, carbs, and fat, see the macro calculator.

Accuracy and limitations

Mifflin-St Jeor is a population-average equation. Individual BMR can vary by roughly ±10% from the prediction due to:

• Body composition. Muscle burns more calories at rest than fat, so a muscular person has a higher BMR than the equation predicts at the same weight. Dedicated body-composition-based equations (Katch-McArdle, Cunningham) perform better for lean, trained individuals.
• Genetics. BMR varies by a few percent between individuals with identical measurable characteristics.
• Thyroid and hormonal status. Hypothyroidism, hyperthyroidism, and some medications shift BMR significantly.
• Adaptive thermogenesis. Prolonged calorie restriction lowers BMR below the predicted value — the body adapts to a deficit.

Related calculators

• TDEE calculator — BMR plus activity for total daily calorie needs.
• Macro calculator — protein, carb, and fat split from TDEE.
• Body fat % estimator — for body-composition context when lean mass is high.

Medical disclaimer. This calculator is for general educational use and is not medical advice. BMR and calorie estimates are based on population averages and do not account for medical conditions, medications, or individual metabolic variation. Consult a qualified healthcare professional or registered dietitian for clinical or therapeutic nutrition planning.