What RMR means
Your resting metabolic rate (RMR) is the energy your body uses at rest just to keep you alive — breathing, circulation, cell repair. It's the biggest piece of your daily calorie burn. The Mifflin-St Jeor estimate is 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women). A 30-year-old, 80 kg, 180 cm man lands near 1,780 calories. The stricter, fasted-and-rested version of this figure is the BMR calculator.
How to use this calculator
Enter sex (1 male, 0 female), age, weight in kg and height in cm. The result is your estimated resting burn. To get total daily calories, multiply by an activity factor — see the maintenance calorie calculator.
RMR vs. BMR
RMR and BMR are often used interchangeably and differ only slightly: BMR is measured under stricter overnight-fasted lab conditions, while RMR is measured at rest more loosely and runs a touch higher. The Mifflin-St Jeor equation is a reliable estimate of both. Compare with the Harris-Benedict equation.
What changes your RMR
More muscle raises RMR; aging and weight loss lower it. The estimate is an average — actual rates vary by body composition and genetics. For general information only, not medical advice.
Frequently asked questions
- How do I calculate RMR?
- Use the Mifflin-St Jeor equation: 10 × weight(kg) + 6.25 × height(cm) − 5 × age, then +5 for men or −161 for women.
- What is the difference between RMR and BMR?
- They're nearly the same. BMR is measured under stricter fasted conditions; RMR is measured at rest and is slightly higher. Both estimate resting calorie burn.
- How do I turn RMR into total daily calories?
- Multiply RMR by an activity factor (1.2–1.9) to get your total daily energy expenditure.
- What lowers my RMR?
- Aging, losing weight and losing muscle all reduce it; building muscle raises it.
- Do I need to fast before using this calculator?
- No. The calculator applies an equation rather than measuring you, so it only needs age, sex, weight and height. Fasting matters for lab tests such as indirect calorimetry, which measure your actual resting burn.