Resting metabolic rate, or RMR, is the number of calories your body burns while you do nothing. It is the foundation of any estimate of daily energy needs, because everything else, from walking to workouts, is added on top of it. Laboratories measure RMR with a breathing mask or hood that records oxygen use, but most people rely on prediction equations. Several are in common use, and they do not give identical answers. This calculator applies four of the best known equations to your age, sex, height and weight, shows each one, and reports their average and range so you can see how much uncertainty there is.
How to use the RMR calculator
- Select your sex and enter your age. The calculator is for adults 18 and over.
- Enter your height and weight in any units; they are converted for you.
- Compare the four results. If they cluster within 100 kcal, you can be fairly confident. A wide spread means a larger error is possible.
- Use the average, or Mifflin-St Jeor, as a working figure, then multiply by an activity level with the TDEE Calculator.
RMR formulas
W is weight in kilograms, H height in centimetres and A age in years; results are in kcal per day.
Owen: men 879 + 10.2 W · women 795 + 7.18 W
Schofield (WHO 1985), men: 18–29 y 0.063 W + 2.896 · 30–59 y 0.048 W + 3.653 · 60+ y 0.049 W + 2.459 (MJ/day)
Schofield, women: 18–29 y 0.062 W + 2.036 · 30–59 y 0.034 W + 3.538 · 60+ y 0.038 W + 2.755 (MJ/day)
Harris-Benedict (revised), men: 88.362 + 13.397 W + 4.799 H − 5.677 A · women: 447.593 + 9.247 W + 3.098 H − 4.330 A
Schofield values are in megajoules per day and are converted to kilocalories by dividing by 4.184 × 10−3. Sources: Mifflin MD et al., Am J Clin Nutr 1990;51:241–247; Owen OE et al., Am J Clin Nutr 1986;44:1–19 (women) and 1987;46:875–885 (men); Schofield WN, Hum Nutr Clin Nutr 1985;39C(suppl 1):5–41, as adopted in the FAO/WHO/UNU report on energy and protein requirements (1985); Roza AM, Shizgal HM, Am J Clin Nutr 1984;40:168–182.
Worked example
A 35-year-old woman, 168 cm, 65 kg.
- Mifflin-St Jeor: 650 + 1,050 − 175 − 161 = 1,364 kcal
- Owen: 795 + 7.18 × 65 = 1,262 kcal
- Schofield: (0.034 × 65 + 3.538) MJ = 5.748 MJ = 1,374 kcal
- Revised Harris-Benedict: 1,418 kcal
- Average 1,354 kcal; range 1,262 to 1,418 kcal.
RMR for sample adults aged 35
| Sex (age 35) | Weight | Mifflin-St Jeor | Owen | Schofield (WHO) | Harris-Benedict revised |
|---|---|---|---|---|---|
| Woman | 50 kg | 1,195 | 1,154 | 1,252 | 1,270 |
| Man | 50 kg | 1,442 | 1,389 | 1,447 | 1,414 |
| Woman | 60 kg | 1,295 | 1,226 | 1,333 | 1,362 |
| Man | 60 kg | 1,542 | 1,491 | 1,561 | 1,548 |
| Woman | 70 kg | 1,395 | 1,298 | 1,414 | 1,455 |
| Man | 70 kg | 1,642 | 1,593 | 1,676 | 1,682 |
| Woman | 80 kg | 1,495 | 1,369 | 1,496 | 1,547 |
| Man | 80 kg | 1,742 | 1,695 | 1,791 | 1,816 |
| Woman | 90 kg | 1,595 | 1,441 | 1,577 | 1,639 |
| Man | 90 kg | 1,842 | 1,797 | 1,906 | 1,950 |
Why the equations differ
- Different populations. Owen used US women and men of varied weight; Schofield pooled many studies mostly from Europe and North America in the 1980s; Mifflin sampled a later, heavier population.
- Different inputs. Owen and Schofield use weight (and age bands) only; Mifflin and Harris-Benedict add height.
- Age trends. Equations with age as a continuous term give gradual declines; Schofield uses age bands that step down.
- Body composition. Lean mass is the best single predictor of RMR, and none of these equations knows yours. For lean-mass-based estimates see the BMR Calculator.
Using your RMR
RMR is the floor of your energy needs, not a target. Total daily energy is RMR times a physical activity level; the Calorie Calculator and Maintenance Calorie Calculator do that, and the Mifflin-St Jeor Calculator and Harris-Benedict Calculator look at single equations in detail. Eating well below RMR for long periods is difficult and best done only with professional supervision.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian about your own needs.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247.
- Owen OE, et al. A reappraisal of caloric requirements in healthy women. Am J Clin Nutr 1986;44:1–19. A reappraisal of the caloric requirements of men. Am J Clin Nutr 1987;46:875–885.
- Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr 1985;39(Suppl 1):5–41.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr 1984;40:168–182.
- Frankenfield D, et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc 2005;105:775–789.
Frequently asked questions
What is resting metabolic rate?
RMR is the energy your body uses at rest to keep you alive: breathing, circulation, cell repair and temperature control. It is the largest part of daily energy use for most people, typically 60 to 75 percent of the total, with activity and digestion making up the rest.
What is the difference between RMR and BMR?
Basal metabolic rate is measured under strict conditions: after an overnight fast, fully rested, in a thermoneutral room. Resting metabolic rate is measured under less strict conditions and is usually a little higher. The equations on this page were fitted to resting measurements, and in practice the two terms are used almost interchangeably.
Which RMR equation should I trust?
Mifflin-St Jeor was found the most accurate in a 2005 review for the Academy of Nutrition and Dietetics (Frankenfield et al., J Am Diet Assoc 105:775–789). The WHO Schofield equations are the international reference, while Owen uses weight only. Looking at the spread of all four is a good reminder of the uncertainty.
How accurate are prediction equations?
For most healthy people they land within about 10 percent of a measured value, but an individual can be off by 15 to 20 percent. Indirect calorimetry in a clinic or lab is the only direct measure.
Can I raise my RMR?
Modestly. Resting energy rises with lean mass, so resistance training and enough protein help to maintain it, particularly during weight loss and ageing. Claims that foods or supplements significantly raise RMR are not supported by good evidence.