BMR Calculator
Calculate your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest.
About the BMR Calculator
Basal Metabolic Rate is the number of calories your body burns just to stay alive at complete rest — breathing, circulating blood, maintaining organ function — before any movement or digestion is factored in. This calculator computes BMR using the Mifflin-St Jeor equation, one of the most accurate and widely validated formulas available.
How It Works
The calculator plugs your weight in kilograms, height in centimeters, age, and sex into the Mifflin-St Jeor formula, which was developed from measured metabolic data and adjusts differently for male and female bodies to reflect typical differences in body composition.
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + (5 if male, −161 if female).
Worked example
Scenario: A 30-year-old man, 70 kg and 175 cm.
- 10 × weight: 10 × 70 = 700.
- 6.25 × height: 6.25 × 175 = 1,093.75.
- −5 × age: −5 × 30 = −150; add +5 for men (−161 for women).
- BMR = 700 + 1,093.75 − 150 + 5 = 1,648.75 kcal a day.
Result: A BMR of about 1,649 kcal a day, or roughly 69 kcal an hour at rest.
Tips and common mistakes
- BMR is energy at complete rest; multiply by an activity factor (TDEE Calculator) for daily needs.
- The same person as a woman would have a BMR 166 kcal lower (1,482.75 kcal).
- Results are for adults 18 and over; the equation wasn't developed for children.
Assumptions & Limitations
- Uses the Mifflin-St Jeor equation, generally considered more accurate for most adults than the older Harris-Benedict formula.
- Assumes typical body composition for the given sex — very muscular or very high body-fat individuals may see somewhat different real BMR.
- BMR does not account for activity — use the TDEE Calculator to estimate total daily calorie burn including movement and exercise.
- Formula-based BMR is an estimate; direct metabolic testing is more accurate for individuals with unusual body composition.
How to interpret a BMR estimate
BMR equations estimate resting energy needs from population data; they do not directly measure your metabolism. The Mifflin–St Jeor equation is a commonly used predictive equation, but individual error is possible because body composition, health status, genetics and measurement conditions vary.
Use BMR as a starting point. For everyday calorie planning, Total Daily Energy Expenditure (TDEE) is usually more useful because it adds an activity estimate. Clinical indirect calorimetry is more individualized when a precise resting-energy measurement is medically necessary.
Sources and review
Method: Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (men) or − 161 (women).
Sources:
- Mifflin MD, St Jeor ST, et al. American Journal of Clinical Nutrition, 1990;51(2):241–247.
Last reviewed: October 2026 by Faheem Ali, founder of CalculatorAnything. The method and examples are provided for transparency; results remain estimates and may contain errors.
Results are estimates for general information and screening, not a diagnosis or medical advice. Talk to a qualified healthcare professional before making health or diet decisions. Spotted an error? Tell us — see our editorial policy for how corrections are handled.