BMR Calculator

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to keep core processes running: breathing, heartbeat, temperature regulation, and cell repair. Think of it as the minimum energy bill your body pays every day before you move a muscle. A 35-year-old woman at 5 ft 5 in and 140 lb has a BMR of about 1,330 calories.

The calculator defaults to Mifflin-St Jeor (1990), which research consistently shows is the most accurate formula for the general adult population, landing within 10% of measured values in about 82% of cases. Harris-Benedict (revised 1984) is older and tends to overestimate. Katch-McArdle skips sex and age entirely and works from lean body mass, making it the best choice if you know your body fat percentage from a DEXA scan or skinfold test.

Both Mifflin-St Jeor and Harris-Benedict use sex-specific constants because men and women differ in average body composition. Men typically carry more lean muscle mass relative to fat at the same height and weight, and muscle tissue burns more calories at rest than fat. The Katch-McArdle formula bypasses sex entirely by working directly from lean mass.

BMR is what you burn at complete rest. TDEE (Total Daily Energy Expenditure) is what you actually burn across a full day, including movement, exercise, and the energy cost of digesting food. TDEE is typically BMR multiplied by an activity factor ranging from about 1.2 (desk job, no exercise) to 1.9 (hard physical labor plus daily training). To find your TDEE, use the Calorie Calculator.

Yes. Adults tend to lose roughly 1-2% of BMR per decade after age 30, driven mainly by gradual loss of muscle mass. In Mifflin-St Jeor the age term subtracts 5 calories per year for both men and women, which reflects this downward trend. Resistance training is the most effective way to preserve lean mass and slow the decline.