BMR Calculator

Frequently Asked Questions

What is BMR and how is it calculated?

Basal Metabolic Rate (BMR) is the number of calories your body requires at complete rest to maintain basic life functions — breathing, circulation, cell production, and temperature regulation. The most widely validated formula is the Mifflin–St Jeor equation (1990): for men, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161.

What is TDEE and how is it different from BMR?

Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day, accounting for your activity level. TDEE = BMR × Activity Multiplier. Activity multipliers range from 1.2 (sedentary — little or no exercise) to 1.9 (extra active — very hard exercise or a physical job). BMR represents the floor; TDEE represents realistic daily needs.

What is the difference between Mifflin–St Jeor and Harris-Benedict?

Both formulas estimate BMR from weight, height, age, and sex. The Mifflin–St Jeor equation (1990) is generally preferred for the general population because it was validated against indirect calorimetry in healthy adults and tends to be more accurate on average. The Harris-Benedict equation was first published in 1919 and revised by Roza and Shizgal in 1984. It typically produces slightly higher estimates (around 2–5% higher). This calculator uses Mifflin–St Jeor as primary and shows Harris-Benedict for comparison.

How do I choose my activity level?

Sedentary (×1.2): desk job, little or no intentional exercise. Lightly active (×1.375): light exercise 1–3 days per week. Moderately active (×1.55): moderate exercise 3–5 days per week. Very active (×1.725): hard exercise 6–7 days per week. Extra active (×1.9): very intense daily exercise or a physically demanding job. Most people overestimate their activity level — when in doubt, choose one level lower.

Is BMR accurate for athletes?

Population-derived BMR formulas are less accurate for athletes and individuals with unusually high or low muscle mass. Muscle tissue has a higher metabolic rate than fat tissue. Athletes with very high muscle mass may have a true BMR higher than formula predictions; individuals with low muscle mass may have a lower true BMR. For athletes, measured resting metabolic rate (via indirect calorimetry) provides more accurate results.

Can I use this BMR calculator for weight management?

TDEE provides a useful starting point for setting calorie targets. To lose weight, a calorie intake below TDEE creates a deficit; to gain weight, a surplus above TDEE is required. A common guideline is a deficit or surplus of 300–500 kcal/day for gradual, sustainable change. However, this calculator provides estimates based on population averages — individual responses vary. Always consult a registered dietitian or healthcare professional before making significant dietary changes.