🔥 BMR Calculator
Calculate your Basal Metabolic Rate (BMR) - the calories your body burns at complete rest to maintain basic life functions.
What is BMR (Basal Metabolic Rate)?
Your Basal Metabolic Rate (BMR) represents the minimum number of calories your body needs to maintain basic physiological functions while at complete rest. These functions include:
- Breathing and oxygen circulation
- Heart beating and blood circulation
- Cell production and repair
- Body temperature regulation
- Brain and nervous system function
- Digestive system maintenance
BMR accounts for approximately 60-75% of your total daily calorie expenditure, making it the largest component of your metabolism.
BMR Formulas Explained
We use two scientifically validated equations to calculate BMR:
Mifflin-St Jeor Equation (1990)
Considered the most accurate formula for most people:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Harris-Benedict Equation (Revised 1984)
The classic formula, still widely used:
Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)
Factors That Affect BMR
| Factor | Effect on BMR |
|---|---|
| Age | BMR decreases 2-3% per decade after age 20 |
| Gender | Men typically have 5-10% higher BMR than women |
| Body Composition | More muscle = higher BMR; more fat = lower BMR |
| Genetics | Can account for 5-10% variation between individuals |
| Hormones | Thyroid hormones significantly impact metabolic rate |
| Temperature | Extreme temperatures can increase BMR by 10-20% |
How to Use Your BMR
Once you know your BMR, you can calculate your Total Daily Energy Expenditure (TDEE) by multiplying BMR by an activity factor:
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | × 1.2 | Little to no exercise, desk job |
| Lightly Active | × 1.375 | Light exercise 1-3 days/week |
| Moderately Active | × 1.55 | Moderate exercise 3-5 days/week |
| Very Active | × 1.725 | Hard exercise 6-7 days/week |
| Extremely Active | × 1.9 | Very hard exercise, physical job |
Worked Examples
Example 1: 30-Year-Old Male
John is 30 years old, 180 cm tall, and weighs 80 kg.
Using Mifflin-St Jeor:
BMR = (10 × 80) + (6.25 × 180) - (5 × 30) + 5
BMR = 800 + 1125 - 150 + 5 = 1,780 calories/day
Example 2: 25-Year-Old Female
Sarah is 25 years old, 165 cm tall, and weighs 60 kg.
Using Mifflin-St Jeor:
BMR = (10 × 60) + (6.25 × 165) - (5 × 25) - 161
BMR = 600 + 1031.25 - 125 - 161 = 1,345 calories/day
References
- Mifflin, M. D., et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 51(2), 241-247.
- Harris, J. A., & Benedict, F. G. (1918). A Biometric Study of Human Basal Metabolism. Proceedings of the National Academy of Sciences, 4(12), 370-373.
- Frankenfield, D., et al. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. Journal of the American Dietetic Association, 105(5), 775-789.
- NIH. (2025). Body Weight Planner. National Institute of Diabetes and Digestive and Kidney Diseases.
Disclaimer: This calculator provides estimates for educational purposes. Consult healthcare professionals for personalized advice.