Resting metabolic rate (RMR) is the energy your body uses at rest, measured under less strict conditions than basal metabolic rate (BMR). It runs a few percent higher than BMR, and the Mifflin–St Jeor equation was derived from RMR measurements: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, then +5 for men or −161 for women. For a 35-year-old woman at 5′5″ and 165 lb that is about 1,444 kcal.
Key takeaways
- RMR and BMR are close, and equation-based calculators treat them as the same number.
- Mifflin–St Jeor was built from measured resting energy, so it is a natural fit for an RMR estimate.
- RMR is not your daily calorie burn; multiply by an activity factor to get TDEE.
- Indirect calorimetry measures RMR from your breath and is the way to check whether an equation fits you.
How does this RMR calculator work?
Enter your sex, age, weight and height and the calculator estimates your resting energy with several equations at once: Mifflin–St Jeor, Harris–Benedict and, if you add body fat, the lean-mass equations Katch–McArdle and Cunningham. It then multiplies the result by five activity levels so you can see your TDEE. The equations and results are the same as on the BMR calculator, so this page focuses on what is specific to RMR.
What is RMR, and how is it different from BMR?
BMR is the minimum energy needed to keep you alive, measured after sleep, after fasting and in a calm, comfortable room. RMR is measured at rest but under looser conditions, so it picks up a little extra energy use and runs a few percent higher. In everyday use, the two terms are interchangeable. The full comparison, with TDEE, is in TDEE vs BMR vs RMR.
| Measure | BMR | RMR |
|---|---|---|
| Measured | Strict, after sleep and fasting | Rested but less strict |
| Value | Slightly lower | Slightly higher, a few percent |
| Used in calculators | Interchangeably with RMR | Interchangeably with BMR |
Which equation estimates RMR best?
The Mifflin–St Jeor equation was derived from measurements of resting energy expenditure in healthy people (Mifflin et al., 1990), which is why it matches RMR so well. A systematic review comparing predictive equations found it estimated measured resting energy within 10% in more people than the alternatives, both with and without obesity (Frankenfield et al., 2005).
Men: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 Women: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Worked example
A 35-year-old woman who is 5′5″ (165 cm) and weighs 165 lb (74.8 kg).
| Equation | Estimated RMR |
|---|---|
| Mifflin–St Jeor | 1,444 kcal |
| Harris–Benedict (revised) | 1,500 kcal |
| Harris–Benedict (original) | 1,513 kcal |
The Harris–Benedict equations (Harris & Benedict, 1918; Roza & Shizgal, 1984) run 4–5% higher for her. A 30-year-old man at 5′10″ and 190 lb (86.2 kg) gets 1,828 kcal from Mifflin–St Jeor. Her TDEE at a moderate activity level (× 1.55) is 2,239 kcal. The maintenance calorie calculator takes it from there.
When should I get my RMR measured?
Equations estimate the average for people like you, and an individual can differ by 10% or more. A measurement is worth considering when:
- your weight trend does not match your calculated TDEE after 2–4 weeks of careful logging;
- you have a medical condition or take medication that may affect metabolism (ask your doctor);
- you are a serious athlete or have lost a large amount of weight, where measured energy use can sit below what body size predicts (Trexler et al., 2014).
The measurement is called indirect calorimetry. You rest quietly, usually for 10–30 minutes, while a mask or hood captures your breath. The device measures oxygen consumed and carbon dioxide produced and calculates energy use. Fast, rest and avoid caffeine and hard exercise beforehand as the clinic instructs.
RMR, lean mass and the Katch–McArdle equation
Resting energy follows lean mass closely, which is why equations using it can fit very lean or muscular people better (McArdle, Katch & Katch). If you know your body fat, enter it to see them, or estimate it with the body fat calculator and the lean body mass calculator.
What should I do with my RMR?
Use it to understand your baseline, then work with TDEE. RMR times an activity factor gives TDEE, and your weight trend confirms it; the adaptive TDEE calculator automates that. Do not plan to eat below your RMR for long without medical supervision.
Frequently asked questions
What is the difference between RMR and BMR?
BMR is measured under strict conditions after sleep and fasting, in a thermoneutral room. RMR is measured at rest under looser conditions, so it runs slightly higher. In practice, the same equations are used for both, and the numbers are close enough for planning. See the BMR calculator.
How do I calculate my RMR?
Use Mifflin–St Jeor: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. A 35-year-old woman at 165 lb and 5′5″ gets 1,444 kcal. The calculator also shows other equations side by side.
What is a good RMR?
There is no good or bad number. RMR mostly reflects body size and lean mass, so larger and more muscular people have higher values. Compare your result with the equation estimate rather than with other people.
How is RMR actually measured?
Indirect calorimetry. You breathe into a mask or hood for 10–30 minutes while resting, and the device measures oxygen use and carbon dioxide output, from which it calculates energy expenditure. It is offered at some clinics, universities and gyms.
Should I get my RMR tested?
It can help if your weight trend does not match your calculated numbers, if you have a medical condition that affects metabolism, or if you are a serious athlete. For most people, tracking weight and intake for 2–4 weeks gives a practical answer for free.
Can I eat my RMR to lose weight?
No. RMR is what you burn at rest, and your total daily burn is higher. Set a deficit from TDEE instead and do not eat below RMR for long without medical supervision.
References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2):241–247.
- Frankenfield D, Roth-Yousey L, Compher C (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association 105(5):775–789.
- Harris JA, Benedict FG (1918). A biometric study of human basal metabolism. Proceedings of the National Academy of Sciences 4(12):370–373.
- Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition 40(1):168–182.
- Trexler ET, Smith-Ryan AE, Norton LE (2014). Metabolic adaptation to weight loss: implications for the athlete. Journal of the International Society of Sports Nutrition 11:7.
- McArdle WD, Katch FI, Katch VL (2015). Exercise Physiology: Nutrition, Energy, and Human Performance (8th ed.). Wolters Kluwer Health.