Health

RMR Calculator

Calculate your resting metabolic rate using three validated formulas and compare results.

Quick Answer

A 30-year-old male, 170 cm, 70 kg burns roughly 1,650-1,700 calories/day at rest. Your actual TDEE (including activity) is typically 1.4-2.2x your RMR.

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Disclaimer: RMR estimates are approximations based on population averages. Individual metabolism varies based on genetics, thyroid function, body composition, and other factors. For precise RMR measurement, consider indirect calorimetry testing. This is not medical or dietary advice.

About This Tool

The RMR Calculator estimates your resting metabolic rate using three well-validated formulas. By comparing the Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle equations side by side, you get a range rather than a single number, which better represents the inherent uncertainty in metabolic estimates.

Understanding your RMR is the foundation of nutrition planning. Whether your goal is weight loss, maintenance, or muscle gain, knowing how many calories your body needs at rest gives you a baseline to work from. Multiply your RMR by an activity factor to get your total daily energy expenditure (TDEE), then adjust calories above or below that number based on your goals.

Frequently Asked Questions

What is resting metabolic rate (RMR)?
RMR is the number of calories your body burns at complete rest to maintain basic functions -- breathing, circulation, cell production, and temperature regulation. It accounts for 60-75% of total daily energy expenditure. RMR is slightly higher than basal metabolic rate (BMR) because it includes minor movements and the thermic effect of food.
Which RMR formula is most accurate?
The Mifflin-St Jeor equation is generally considered the most accurate for most adults. The Katch-McArdle formula is best if you know your body fat percentage, as it accounts for lean body mass. Harris-Benedict (revised) is the oldest and tends to overestimate slightly. Using all three gives you a range rather than relying on a single estimate.
How does RMR relate to weight loss?
To lose weight, you need to consume fewer calories than your total daily energy expenditure (TDEE). TDEE = RMR x activity multiplier. Eating below your RMR for extended periods can trigger metabolic adaptation, slowing your metabolism. Most experts recommend a deficit of 300-500 calories below TDEE, not below RMR, for sustainable fat loss.
What factors affect RMR?
Muscle mass is the biggest factor -- more muscle means higher RMR. Age decreases RMR about 1-2% per decade after 20. Men generally have higher RMR than women due to more muscle mass. Genetics play a role (variation of 100-200 cal/day between similar people). Thyroid function, body temperature, caffeine, and recent meals also affect RMR.
Can I increase my RMR?
The most effective way is building lean muscle through resistance training -- each pound of muscle burns about 6 calories/day at rest vs 2 for fat. High-intensity interval training (HIIT) also temporarily elevates RMR for hours after exercise (EPOC effect). Adequate protein intake supports muscle maintenance. Crash dieting and excessive cardio can lower RMR.

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