Metabolic Rate Calculator
The Energy Cost of Simply Being Alive
Even lying perfectly still in a warm room, the body burns a substantial number of calories just running its baseline operations — heartbeat, breathing, cell repair, temperature regulation. That baseline, basal metabolic rate (BMR), is the foundation every calorie-planning calculation starts from, since activity is added on top of it, not instead of it.
The Formula
Female: BMR = 10W + 6.25H − 5A − 161
This is the Mifflin-St Jeor equation, where W is weight in kilograms, H is height in centimeters, and A is age in years. It's widely regarded as more accurate for modern populations than the older Harris-Benedict formula.
Where This Calculation Matters
- Nutrition and diet planning — BMR is multiplied by an activity factor to estimate total daily energy needs for weight maintenance, loss, or gain.
- Clinical nutrition support — hospitals use BMR-based estimates to set caloric targets for patients unable to eat normally.
- Athletic training programs — coaches use metabolic rate estimates to plan caloric intake around training load.
- Comparative physiology — BMR normalized by body size is used to compare metabolic efficiency across individuals.
Worked Examples
| Profile | Weight | Height | Age | BMR |
|---|---|---|---|---|
| Male | 70 kg | 175 cm | 30 yr | 1,648.75 kcal/day |
| Female | 60 kg | 165 cm | 30 yr | 1,320.25 kcal/day |
| Male | 90 kg | 180 cm | 45 yr | 1,805.00 kcal/day |
BMR represents calories burned at complete rest over 24 hours; total daily energy expenditure with normal activity is typically 1.2 to 1.9 times this baseline.
How to Use This Calculator
- Select biological sex (male or female), since the formula constant differs.
- Enter Weight (kg), Height (cm), and Age (years).
- Select Calculate to get the estimated basal metabolic rate in kcal/day.
Related Calculations
Interested in the plant-side counterpart of energy production rather than consumption? See the Photosynthesis Rate Calculator. For the enzyme kinetics that drive individual metabolic reactions, use the Enzyme Rate Calculator.