BMR Calculator

A BMR calculator estimates your Basal Metabolic Rate, the number of calories your body burns at complete rest to keep basic functions like breathing, circulation, and cell repair running. This tool uses the Mifflin-St Jeor equation, which is widely regarded as the most accurate predictive formula for healthy adults and has largely replaced the older Harris-Benedict equation. The formula is BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(years) + s, where s is +5 for men and -161 for women. Your BMR alone is not your daily calorie target, because almost no one lies in bed all day. To get Total Daily Energy Expenditure (TDEE), the calculator multiplies BMR by an activity factor: roughly 1.2 for sedentary, 1.375 for light activity, 1.55 for moderate, 1.725 for very active, and 1.9 for extremely active. TDEE is the practical number, the calories you burn on a typical day and therefore roughly what you would eat to maintain your current weight. From there the tool derives goal targets. A deficit of about 500 calories per day corresponds to roughly one pound (0.45 kg) of fat loss per week, since a pound of body fat stores about 3,500 calories, while a modest surplus of 250 to 500 calories supports lean muscle gain. Treat these as starting estimates, not precise prescriptions: real metabolism varies with body composition, genetics, and how accurately you log food and movement. All inputs are processed in your browser, so your age, height, and weight are never transmitted or stored.