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 a 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 This BMR / Calories
- 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.
The Formula Explained
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.