BMR Calculator (Mifflin-St Jeor)
Basal Metabolic Rate (BMR) is the number of calories your body burns each day at complete rest, just to maintain basic physiological functions. It is the foundation of any calorie plan because it represents your minimum energy requirement. The Mifflin-St Jeor equation, published in 1990 and validated in multiple subsequent studies, is considered the most accurate predictive equation for BMR in the general population. It uses your weight in kilograms, height in centimetres, age in years, and sex. For men the formula adds 5 to the base value; for women it subtracts 161. Enter your measurements to calculate your BMR and the approximate number of calories you would need if you were completely sedentary.
Mifflin-St Jeor formula
Men: BMR = 10 * weight(kg) + 6.25 * height(cm) - 5 * age + 5
Women: BMR = 10 * weight(kg) + 6.25 * height(cm) - 5 * age - 161
BMR per hour = BMR / 24
Published in the Journal of the American Dietetic Association (Mifflin et al., 1990). Coefficients: weight 10 kcal/kg, height 6.25 kcal/cm, age -5 kcal/year, sex constant +5 (men) or -161 (women).
Worked example
- Male, 30 years, 75 kg, 175 cm.
- BMR = (10 * 75) + (6.25 * 175) - (5 * 30) + 5
- = 750 + 1,093.75 - 150 + 5 = 1,698.75 kcal/day
- Female, 30 years, 60 kg, 165 cm.
- BMR = (10 * 60) + (6.25 * 165) - (5 * 30) - 161
- = 600 + 1,031.25 - 150 - 161 = 1,320.25 kcal/day
BMR calculator: frequently asked questions
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the number of calories your body requires at complete rest to maintain vital functions: breathing, circulation, cell production, nutrient processing, protein synthesis, and temperature regulation. BMR accounts for approximately 60-70% of total daily energy expenditure in sedentary individuals.
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation (1990) calculates BMR from weight, height, age, and sex. 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. Studies have found it to be more accurate than the older Harris-Benedict equation for most individuals.
How is BMR different from TDEE?
BMR is your calorie need at complete rest with no movement. TDEE (Total Daily Energy Expenditure) adds activity-related calorie burn: TDEE = BMR * activity multiplier (ranging from 1.2 for sedentary to 1.9 for very active). TDEE is the number used for weight management calorie planning.
Does BMR change with age?
Yes. BMR typically declines with age, primarily due to loss of lean muscle mass (sarcopenia). After age 30, BMR decreases by approximately 2-3% per decade. Maintaining muscle mass through resistance training can partially offset this decline.
Can I increase my BMR?
Yes, to some degree. Building lean muscle mass through resistance training is the most effective way to increase resting metabolic rate, since muscle tissue burns more calories at rest than fat tissue. Adequate protein intake supports muscle preservation. Very low calorie diets can lower BMR through metabolic adaptation.
Official sources
- NIH: NIDDK Weight Management Resources.
- USDA Dietary Guidelines 2020-2025: DietaryGuidelines.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.