BMR Calculator

BMR is the number of calories your body burns at complete rest — the minimum energy required to keep you alive (breathing, circulation, organ function, cell repair). It accounts for 60–75% of your total daily calorie burn. Age, sex, height, and weight all affect BMR. Muscle mass raises it; fat mass raises it less. BMR decreases with age (roughly 1–2% per decade after 20).

BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is your total daily calorie burn including all activity. TDEE = BMR × Activity Multiplier. For most people, TDEE is 1.3–1.9× their BMR. To maintain weight, eat at TDEE. To lose weight, eat below TDEE. To gain muscle, eat above TDEE.

The Mifflin-St Jeor equation (1990) is the most accurate for most people, with a mean error of ±10%. It's recommended by the American Dietetic Association. The original Harris-Benedict equation (1919) tends to overestimate BMR by 5%. The revised Harris-Benedict (1984) is more accurate than the original but still slightly less precise than Mifflin-St Jeor. This calculator uses Mifflin-St Jeor as the primary formula and shows Harris-Benedict for comparison.

To lose weight, create a calorie deficit below your TDEE. A deficit of 500 calories/day = approximately 1 lb/week of fat loss (3,500 cal = 1 lb). Never eat below your BMR for extended periods — it can slow metabolism, cause muscle loss, and nutrient deficiencies. A safe approach: eat at TDEE minus 15–20%, which gives sustainable fat loss without metabolic adaptation.

Males generally have higher BMR because they have more lean muscle mass relative to body weight, and muscle tissue burns more calories at rest than fat tissue. On average, males have 10–15% higher BMR than females of the same age, height, and weight. This is why sex is a variable in all BMR formulas.

Yes significantly. A pound of muscle burns approximately 6 calories/day at rest, while a pound of fat burns only 2 calories/day. This is why resistance training — which builds muscle — raises your BMR over time. Two people with the same weight but different body compositions can have BMRs that differ by 200–300 calories/day.

Sedentary (desk job, no exercise): BMR × 1.2. Lightly active (light exercise 1–3 days/week): BMR × 1.375. Moderately active (moderate exercise 3–5 days/week): BMR × 1.55. Very active (hard exercise 6–7 days/week): BMR × 1.725. Extra active (physical job + hard exercise daily): BMR × 1.9. Most office workers are sedentary to lightly active.