Basal Metabolic Rate is the number of calories your body burns at complete rest — maintaining temperature, circulation, and organ function. It represents the minimum energy your body needs to survive. Multiply BMR by an activity multiplier to get your Total Daily Energy Expenditure (TDEE), which is the baseline for any calorie goal.
The Mifflin-St Jeor equation (1990) is considered more accurate for most adults and is preferred by nutritionists: Men: (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: (10 × kg) + (6.25 × cm) − (5 × age) − 161. The older Harris-Benedict equation (1919, revised 1984) tends to overestimate by 5%. Both are population averages — individual BMR can vary by ±15% based on genetics, lean mass, and hormonal factors.
BMR is the calories burned at rest. TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor to account for movement, exercise, and the thermic effect of food. TDEE is what you actually burn in a day.
On average, men have higher muscle mass and lower body fat percentage than women at the same weight and age. Muscle tissue burns more calories at rest, so the formulas incorporate a sex-based offset.
Population-level formulas are accurate to within about ±10–15% for individuals. Factors not captured include body composition, genetics, thyroid function, and medication. For precision, use an indirect calorimetry measurement.
Sedentary = desk job, no exercise. Light = 1–3 workouts/week. Moderate = 3–5 workouts/week. Active = hard exercise 6–7 days/week. Very active = physical job plus daily exercise. Most people overestimate their activity level.
See also the Calorie Calculator, BMI Calculator, and Body Fat Calculator.