BMR Calculator
What is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic life functions at complete rest—breathing, circulation, cell production, and nutrient processing.
Related Calculators
Understanding Basal Metabolic Rate
BMR Equations Compared
This calculator offers three scientifically validated equations for calculating BMR. Each has different strengths and use cases.
Mifflin-St Jeor (Recommended)
Considered the most accurate for most people. Developed in 1990.
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161
Harris-Benedict (Revised)
Classic equation from 1919, revised in 1984. Still widely used.
Men: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) - 5.677 × age
Women: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) - 4.330 × age
Katch-McArdle
Most accurate if you know your body fat percentage. Uses lean body mass.
BMR = 370 + 21.6 × lean body mass(kg)
Factors That Affect BMR
- Age: BMR decreases about 2% per decade after 20
- Gender: Men typically have higher BMR due to muscle mass
- Body composition: More muscle = higher BMR
- Body size: Larger bodies burn more calories
- Genetics: Natural variation between individuals
- Hormones: Thyroid function significantly affects BMR
- Diet: Severe restriction can lower BMR
- Temperature: Cold exposure can increase BMR
Activity Multipliers
To find your Total Daily Energy Expenditure (TDEE), multiply your BMR by an activity factor:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little exercise | BMR × 1.2 |
| Lightly Active | Light exercise 1-3 days/week | BMR × 1.375 |
| Moderately Active | Moderate exercise 3-5 days/week | BMR × 1.55 |
| Very Active | Hard exercise 6-7 days/week | BMR × 1.725 |
| Extra Active | Very hard exercise, physical job | BMR × 1.9 |
BMR vs RMR
BMR (Basal Metabolic Rate) is measured under strict conditions: complete rest, 12-hour fast, in a dark room at comfortable temperature.
RMR (Resting Metabolic Rate) is similar but measured under less strict conditions. RMR is typically 10-20% higher than BMR and is more practical to measure.
Important Note
BMR calculations provide estimates based on averages. Individual metabolism can vary by 200-300 calories from predicted values. Use your BMR as a starting point and adjust based on your actual results over time.
Frequently Asked Questions
What is BMR and why does it matter?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, and cell production. It accounts for 60-75% of your total daily calorie expenditure, making it essential for understanding your calorie needs for weight management.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is generally considered most accurate for most people. However, if you know your body fat percentage, the Katch-McArdle formula provides the best estimate since it uses lean body mass. Harris-Benedict is still reliable but slightly less accurate than newer formulas.
How is BMR different from TDEE?
BMR measures calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) includes all calories burned including physical activity. To get TDEE, multiply your BMR by an activity factor (1.2-1.9 depending on activity level).
Can I increase my BMR?
Yes, building muscle mass is the most effective way to increase BMR since muscle tissue burns more calories than fat. Strength training, adequate protein intake, getting enough sleep, and avoiding severe calorie restriction all help maintain or boost your metabolic rate.