Quick Answer
BMR (Basal Metabolic Rate) is most commonly calculated using the Mifflin-St Jeor equation: for men, BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; for women, subtract 161 instead of adding 5.
What Is BMR / Calories?
BMR (Basal Metabolic Rate) is the number of calories your body needs to maintain basic life-sustaining functions, breathing, circulation, cell production, and maintaining body temperature, while completely at rest. It does not include calories burned through physical activity, digestion, or exercise.
BMR typically accounts for 60-75% of total daily calorie expenditure for most people, making it the single largest component of daily energy needs. To get a complete picture of how many calories you burn in a typical day, BMR is multiplied by an activity factor to calculate TDEE (Total Daily Energy Expenditure), this is the number most people actually use for weight management goals.
Several formulas exist to estimate BMR, with the Mifflin-St Jeor equation (developed in 1990) generally considered more accurate for modern populations than the older Harris-Benedict equation (1919, revised 1984). Both use weight, height, age, and sex as inputs, since these are the strongest predictors of basal metabolic rate.
How to Use
- 1Enter your weight, height, age, and biological sex.
- 2The calculator computes your BMR using the Mifflin-St Jeor formula.
- 3Select your activity level (sedentary, lightly active, moderately active, very active) to get your TDEE, total daily calories needed to maintain your current weight.
- 4Use the TDEE figure as a baseline: eat below it for weight loss, at it for maintenance, or above it for weight/muscle gain.
Formula
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161TDEE = BMR × Activity MultiplierSedentary ×1.2, Light ×1.375, Moderate ×1.55, Very Active ×1.725
Example: 30-year-old man, 75 kg, 178 cm, moderately active
- BMR = 10×75 + 6.25×178 − 5×30 + 5
- BMR = 750 + 1112.5 − 150 + 5
- BMR = 1717.5
- TDEE = 1717.5 × 1.55 (moderate activity)
Tips & Things to Know
- BMR alone is not the number to eat at, it's the calories your body needs at complete rest. Use TDEE (BMR × activity multiplier) as your actual daily calorie reference point.
- A common, sustainable approach for weight loss is eating roughly 500 calories below TDEE per day, which targets about 0.5 kg (1 lb) of weight loss per week, extremely aggressive deficits are harder to sustain and can affect muscle mass.
- BMR naturally decreases with age (roughly 1-2% per decade after adulthood) and decreases with muscle loss, which is part of why calorie needs typically decline somewhat as people get older unless activity and muscle mass are maintained.
- These formulas provide population-level estimates, individual metabolic rate can vary due to genetics, muscle mass, hormonal factors, and other variables, so treat the result as a starting point to adjust based on real-world results.