BMR Calculator
Calculate your Basal Metabolic Rate
Quick Facts
- •Average male BMR: 1,600–1,800 kcal/day
- •Average female BMR: 1,400–1,600 kcal/day
- •BMR decreases with age
What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs at complete rest to maintain basic life functions like breathing, circulation, and cell production. It accounts for about 60–75% of your daily calorie expenditure.
BMR Formulas
This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate for most people. For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 5. For women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161.
Understanding the bmr calculator
Basal metabolic rate is the energy your body uses at complete rest to run the brain, heart, liver, kidneys, and everything else. It typically accounts for 60 to 70 percent of total daily energy use, which is why activity alone rarely moves the total as much as people expect.
Worked examples
Mifflin St Jeor for a 40 year old man, 180 cm, 85 kg
- 1BMR = (10 × weight kg) + (6.25 × height cm) - (5 × age) + 5.
- 2(10 × 85) = 850.
- 3(6.25 × 180) = 1125.
- 4(5 × 40) = 200.
- 5850 + 1125 - 200 + 5 = 1780 kcal.
About 1,780 kcal per day at complete rest.
Katch McArdle when body fat is known
- 1Lean body mass = weight × (1 - body fat fraction). At 85 kg and 20 percent fat that is 68 kg.
- 2BMR = 370 + (21.6 × lean mass) = 370 + (21.6 × 68).
- 3370 + 1469 = 1839 kcal.
About 1,840 kcal, slightly higher because this person carries more lean mass than average.
The three common BMR formulas
| Formula | Inputs | Best for |
|---|---|---|
| Mifflin St Jeor | Weight, height, age, sex | General population, current default |
| Harris Benedict (revised) | Weight, height, age, sex | Legacy comparisons, reads a little high |
| Katch McArdle | Lean body mass | Lean or muscular people with a known body fat figure |
Where your resting energy goes
| Organ or tissue | Share of BMR |
|---|---|
| Liver | About 27 percent |
| Brain | About 19 percent |
| Skeletal muscle | About 18 percent |
| Kidneys | About 10 percent |
| Heart | About 7 percent |
| Everything else | About 19 percent |
Muscle burns roughly 13 kcal per kg per day at rest, so adding 5 kg of muscle raises BMR by about 65 kcal, not the hundreds often claimed.
Frequently asked questions
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This calculator is for educational purposes only. Consult a healthcare professional for personalized nutrition advice.