Harris Benedict Calculator

What is BMR?

Basal Metabolic Rate is the number of calories your body burns at complete rest to maintain essential functions — breathing, circulation, temperature regulation, and cellular repair. BMR accounts for 60–70% of total daily calorie expenditure for most sedentary people.

BMR is influenced by body mass, height, age, and sex. Muscle tissue is more metabolically active than fat tissue, so a lean individual of the same weight will have a higher BMR. BMR declines with age, primarily due to the gradual loss of lean muscle mass.

Formula comparison

Original Harris-Benedict (1919): one of the first scientifically derived BMR equations, based on 136 men and 103 women. Tends to slightly overestimate BMR in overweight individuals.

Revised Harris-Benedict (Roza & Shizgal 1984): recalibrated using updated data; closer to the original but with revised coefficients.

Mifflin-St Jeor (1990): derived from a larger and more representative sample. Multiple validation studies show it is the most accurate formula for most adults, with mean errors typically below 5%.

From BMR to TDEE

TDEE = BMR × activity multiplier. Common multipliers: sedentary (×1.2), lightly active (×1.375), moderately active (×1.55), very active (×1.725), extremely active (×1.9). These are rough categories — even within "moderately active" there is a wide range of actual energy expenditure.

TDEE is the calorie level at which your weight stays stable. To lose weight, eat below TDEE; to gain weight, eat above it. A deficit or surplus of 500 kcal/day corresponds to roughly 0.5 kg change per week using the 7,700 kcal/kg approximation.