Short answerYour BMR is the energy your body uses in a day just to keep you alive at complete rest. Most adults land between about 1,100 and 2,100 calories. A 35-year-old woman who is 5'5" and 150 pounds has a BMR of about 1,375; a 40-year-old man who is 5'11" and 187 pounds, about 1,780.
What BMR rate means
BMR stands for basal metabolic rate. "Basal" means the base level: what your body spends on breathing, pumping blood, keeping warm, repairing cells and running your brain, before you move a muscle or digest a bite. The meaning of BMR in plain terms is your body's idle speed.
Researchers measure it under strict conditions. You lie still after a night's sleep, at a comfortable temperature, having not eaten for about 12 hours. That's why BMR is lower than the calories you actually burn in a day. Movement, exercise and digesting food all come on top. To see the full daily figure, use the TDEE calculator, which starts from the same BMR number.
To explain basal metabolic rate with an everyday comparison: a BMR of 1,500 calories a day works out to about 73 watts. That's the power of an old incandescent light bulb, running nonstop, day and night.
RMR meaning, and how it differs from BMR
RMR stands for resting metabolic rate. Read out letter by letter, the R M R meaning is the same, and some studies call it "resting energy expenditure". It measures the same thing as BMR, but under looser conditions: you might have eaten a few hours earlier or just driven to the clinic. So RMR usually comes out slightly higher than BMR.
In practice, most apps, trainers and calculators use the two terms for the same number. The equations on this page were built from resting measurements, so you can read the result as either.
How to calculate BMR
Very few people get their BMR measured in a lab. Instead, a basal metabolic rate calculation uses an equation built from people who were measured. This calculator shows three:
Mifflin-St Jeor (the main result)
Men: 10 × kg + 6.25 × cm − 5 × age + 5
Women: 10 × kg + 6.25 × cm − 5 × age − 161
Published in 1990, this is the one dietitians use most often. In reviews comparing equations against measured values, it came closest for the most people.
Harris-Benedict (revised 1984)
Men: 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age
Women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age
The original version dates from 1919. It tends to come out a little higher than Mifflin-St Jeor, often by 50 to 100 calories.
Katch-McArdle
370 + 21.6 × lean body mass (kg)
This one ignores age and sex and works from lean mass, everything that isn't fat. It suits people who know their body fat percentage, especially very muscular people, for whom the other two can run low.
The BMR equation for men, worked through
Take a 40-year-old man, 180 cm (5'11") and 85 kg (187 lb). With Mifflin-St Jeor: 10 × 85 + 6.25 × 180 − 5 × 40 + 5 = 850 + 1,125 − 200 + 5 = 1,780 calories a day. The revised Harris-Benedict equation gives about 1,864 for the same man. If he has 20% body fat, Katch-McArdle gives 370 + 21.6 × 68 = about 1,839.
For a woman of 35, 165 cm (5'5") and 68 kg (150 lb): 680 + 1,031 − 175 − 161 = about 1,375 with Mifflin-St Jeor, and about 1,436 with Harris-Benedict.
Basal metabolic rate normal range
There's no single normal BMR, because it depends so much on body size. The table below uses the average U.S. adult from CDC body measurements: a man about 5'9" and 199 pounds, and a woman about 5'3½" and 170 pounds.
| Age | Women | Men |
|---|---|---|
| 20 | 1,522 | 1,901 |
| 30 | 1,472 | 1,851 |
| 40 | 1,422 | 1,801 |
| 50 | 1,372 | 1,751 |
| 60 | 1,322 | 1,701 |
| 70 | 1,272 | 1,651 |
| 80 | 1,222 | 1,601 |
Size moves the number more than age. Here's how BMR changes with height and weight at three ages:
| Person | Age 25 | Age 45 | Age 65 |
|---|---|---|---|
| Woman, 160 cm (5'3"), 55 kg (121 lb) | 1,264 | 1,164 | 1,064 |
| Woman, 165 cm (5'5"), 70 kg (154 lb) | 1,445 | 1,345 | 1,245 |
| Woman, 165 cm (5'5"), 90 kg (198 lb) | 1,645 | 1,545 | 1,445 |
| Man, 175 cm (5'9"), 70 kg (154 lb) | 1,674 | 1,574 | 1,474 |
| Man, 178 cm (5'10"), 85 kg (187 lb) | 1,842 | 1,742 | 1,642 |
| Man, 180 cm (5'11"), 110 kg (243 lb) | 2,105 | 2,005 | 1,905 |
So a normal range for most adults runs from about 1,100 to 1,700 for women and 1,450 to 2,100 for men. The calculator's last line compares you with the average-sized person of your sex and age.
Where your BMR goes
Most of your resting energy goes to a few small, busy organs. Based on measured organ energy use, for a typical adult:
- Liver: about 21%. It processes nutrients and clears waste around the clock.
- Brain: about 20%, even though it's only 2% of body weight.
- Skeletal muscle: about 22%. Each kilogram uses little at rest, but there's a lot of it.
- Heart and kidneys: about 9% and 8%. Per kilogram, these two are the most metabolically active tissues in the body.
- Everything else: about 20%, including the gut, lungs, skin and body fat. Fat tissue burns only about 4.5 calories per kilogram a day.
This is also why building muscle raises BMR less than people hope. A kilogram of muscle burns about 13 calories a day at rest, so adding 2 kg of muscle adds roughly 26 calories.
Does BMR drop with age?
The equations take off 5 calories a year (Mifflin-St Jeor), so a 60-year-old's result is 200 lower than a 20-year-old of the same size. But a 2021 study in Science of more than 6,000 people found that metabolism, adjusted for body size, stays remarkably steady from about 20 to 60 and only starts to decline after that.
Most of the slowdown people feel in their 30s and 40s comes from losing some muscle and moving less, not from a slower engine. Strength training and staying active help on both fronts.
How to check your basal metabolic rate
An equation is a good estimate, typically within about 10% for most people, but it can miss by more. To check basal metabolic rate directly:
- Indirect calorimetry measures the oxygen you breathe in and carbon dioxide you breathe out while resting. Some hospitals, sports labs and dietitians offer it.
- Smart scales and fitness watches show a BMR, but they estimate it from the same kind of equations, sometimes with a body fat reading. They don't measure it.
- Your own weight trend is the practical test. If you eat about your estimated daily needs for a few weeks and your weight holds steady, the estimate was close.
What to do with your BMR
Your BMR is the floor of your daily needs, not a target to eat. A few ways to put it to work:
- Protect the muscle behind it. Muscle is a big part of your resting burn, so get enough protein: the macro calculator shows grams a day for your goal.
- Know your body fat? The body recomp calculator uses the same Katch-McArdle equation to plan calories for training and rest days.
- Compare with your age group. Your metabolic age shows whether your body fat is typical for your size and age.
- Plan a cut that keeps your BMR in mind. The weight loss simulator recalculates your BMR as your weight drops, so the goal date stays realistic.
BMR calculator FAQ
What does BMR mean?
BMR stands for basal metabolic rate: the calories your body burns in a day just to stay alive, lying still and fully rested, without digesting a meal. For most adults it's somewhere between 1,100 and 2,100 calories.
What is a normal basal metabolic rate?
For an average-sized U.S. adult, about 1,320 to 1,520 calories a day for women aged 20 to 60, and about 1,700 to 1,900 for men. Smaller people sit lower and larger people higher.
What does RMR mean?
RMR is resting metabolic rate, the calories you burn at rest under less strict conditions than BMR. It's usually a little higher than BMR, and the two words are often used for the same thing.
What is the BMR equation for men?
The Mifflin-St Jeor equation for men is 10 × weight in kg + 6.25 × height in cm − 5 × age + 5. For women, the last number is −161 instead of +5.
Does BMR go down with age?
A large 2021 study found metabolism adjusted for body size stays steady from about 20 to 60 and declines after that. Most of the drop people notice earlier comes from losing muscle and moving less.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr, 1984;40(1):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.
- Wang Z, et al. Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure. Am J Clin Nutr, 2010. Uses Elia's organ metabolic rates (liver 200, brain 240, heart and kidneys 440, muscle 13, fat 4.5 kcal/kg/day).
- Pontzer H, et al. Daily energy expenditure through the human life course. Science, 2021;373(6556):808–812.
- Centers for Disease Control and Prevention, NCHS. FastStats: body measurements.