BMR CalculatorBasal Metabolic Rate: Calories Burned at Rest
Find out how many calories your body burns doing nothing at all. See your BMR from five scientific formulas, how much each organ uses, and how your resting burn changes with age.
Built & medically reviewed by Manzoor Ahmad, Pharmacist & Calculator Developer · Updated
Formulas: Mifflin-St Jeor, Harris-Benedict (revised), Katch-McArdle and Cunningham. Age trend from Pontzer et al., Science 2021.
How do you calculate BMR?
Use the Mifflin-St Jeor equation, the most accurate for most adults: men = 10 × kg + 6.25 × cm − 5 × age + 5, and women use − 161 instead of + 5. A 30-year-old woman who is 165 cm and 65 kg has a BMR of about 1,370 calories a day, the energy her body burns at complete rest. Multiply BMR by your activity level to get your daily calorie needs.
Your body
feet · inches
That’s 57 kcal an hour, or about 0.95 kcal a minute, just to keep you alive.
Where your resting calories go
Approximate share of resting energy by organ for an average adult. Together, your brain and liver burn almost twice as much as all your muscles at rest.
Every major BMR formula
| Formula | BMR | Best for |
|---|
Average BMR by age and sex
Calculated with Mifflin-St Jeor for a woman of 5’4″ (163 cm) and 150 lb (68 kg), and a man of 5’9″ (175 cm) and 180 lb (82 kg), roughly average US adults.
| Age | Women (5’4″, 150 lb) | Men (5’9″, 180 lb) |
|---|---|---|
| 20 | 1,440 kcal | 1,820 kcal |
| 30 | 1,390 kcal | 1,770 kcal |
| 40 | 1,340 kcal | 1,720 kcal |
| 50 | 1,290 kcal | 1,670 kcal |
| 60 | 1,240 kcal | 1,620 kcal |
| 70 | 1,190 kcal | 1,570 kcal |
The BMR formulas we use
The organ breakdown uses resting-energy shares measured in adults by Elia (1992) and Gallagher et al. (1998).
Woman, 30, 165 cm, 65 kg
- 10 × 65 = 650
- 6.25 × 165 = 1,031.25
- 5 × 30 = 150
- BMR = 650 + 1,031.25 − 150 − 161 = 1,370 kcal/day
- That’s 57 kcal an hour. Her brain uses about 275 kcal of it and her liver about 290.
- At 60, with the same body, her BMR would be about 1,220 kcal. That’s 150 kcal less, the equivalent of a small snack a day.
Can you raise your BMR?
- Muscle helps, modestly: each kg of muscle burns about 13 kcal a day at rest, not the 50 kcal often claimed.
- “Metabolism-boosting” foods: green tea, chilli and coffee add 50–100 kcal at most, and only briefly.
- Crash diets lower it: severe restriction can reduce BMR beyond what weight loss alone explains.
- Sleep matters: short sleep is linked to lower energy use and higher appetite.
- Age: large studies show metabolism stays fairly stable from 20 to 60, then declines about 0.7% a year.
Things that change BMR that a formula can’t see
Thyroid hormone is the main driver. Hypothyroidism can lower BMR by 15–40%, and too high a levothyroxine dose raises it. Fever raises BMR by about 10–13% per °C. Stimulants (ADHD medicines, pseudoephedrine, high-dose caffeine) nudge it up. Beta-blockers nudge it down slightly.
If your measured weight trend doesn’t match these numbers by a wide margin, ask your doctor about a TSH blood test before assuming your metabolism is “broken”.
Related calculators
BMR calculator FAQs
BMR (basal metabolic rate) is the number of calories your body burns at complete rest to keep you alive: breathing, circulating blood, running your brain and organs, and maintaining body temperature. It usually makes up 60–70% of the calories you burn each day.
Use the Mifflin-St Jeor equation. Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. Women: the same, but −161 instead of +5. For example, a 30-year-old woman who is 165 cm tall and weighs 65 kg has a BMR of about 1,370 calories.
Most adult women have a BMR of 1,200–1,500 kcal a day and most men 1,500–1,900 kcal a day. Taller, heavier and more muscular people have higher values, and BMR falls slightly with age.
BMR is measured in strict lab conditions: fasted, fully rested and in a neutral temperature. RMR (resting metabolic rate) is measured less strictly and is usually about 10% higher. In everyday use the two terms mean almost the same thing.
No. BMR is only your resting burn. To find the calories you need, multiply BMR by your activity level (1.2–1.9) to get your TDEE. Eating at BMR is a diet, not maintenance.
It’s generally best not to stay below your BMR for long without supervision. It’s hard to get enough nutrients, and very low intakes increase muscle loss and metabolic adaptation. A deficit from your TDEE that keeps intake near or above BMR is more sustainable.
Yes, but less than often claimed. Skeletal muscle burns about 13 kcal per kg per day at rest. Adding 2 kg of muscle raises BMR by only about 25–30 kcal a day. Its bigger benefits are higher activity burn and better blood-sugar control.
Mostly because of loss of muscle and organ mass and lower activity. A large 2021 study in Science found that metabolism adjusted for body size stays stable from about 20 to 60, then declines about 0.7% a year.
Manzoor Ahmad
Pharmacist · Supplement & Nutrition Writer (9+ yrs) · Calculator Developer (13+ yrs)
I’m a practising pharmacist and I build every DexoCalc calculator. Thyroid medicines and stimulants are among the drugs I dispense that most affect metabolism, which is why this BMR tool also covers what a formula can’t see. It also shows how your resting calories split across your organs, which most BMR calculators leave out.
References
- Mifflin MD, et al. Am J Clin Nutr. 1990;51(2):241–247. PubMed
- Roza AM, Shizgal HM. Am J Clin Nutr. 1984;40(1):168–182. PubMed
- Pontzer H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808–812. PubMed
- Gallagher D, et al. Organ-tissue mass measurement allows modeling of REE and metabolically active tissue mass. Am J Physiol. 1998;275(2):E249–E258. PubMed
- Frankenfield D, et al. J Am Diet Assoc. 2005;105(5):775–789. PubMed
Medical disclaimer: BMR results are estimates for healthy adults and are not medical advice. Thyroid conditions, illness, pregnancy and some medicines change metabolism. Talk to your doctor if your weight changes unexpectedly.