What is BMR?
Basal metabolic rate (BMR) is the energy your body needs to stay alive while completely at rest — pumping blood, breathing, keeping your brain, liver and kidneys working, and maintaining body temperature. For most people it accounts for the majority of the calories they burn in a day.
BMR is not how much you should eat. It leaves out digestion, daily movement and exercise. To turn it into a maintenance number, use the TDEE calculator, or get goal targets straight away with the calorie calculator.
BMR formulas compared
| Formula | Uses | Best for |
|---|---|---|
| Mifflin–St Jeor (1990) | Weight, height, age, sex | Most adults — our default |
| Harris–Benedict (1919, revised 1984) | Weight, height, age, sex | Older standard; tends to run slightly high |
| Katch–McArdle | Lean body mass (needs body-fat %) | Lean or muscular people who know their body fat |
In the original study, Harris–Benedict overestimated measured resting energy by about 5%. A later systematic review found Mifflin–St Jeor predicted resting metabolism within 10% of measured values for more people than the other common equations, which is why most dietitians use it today. If you know your body-fat percentage, the calorie calculator can switch to Katch–McArdle.
How BMR changes with age
Mifflin–St Jeor lowers BMR by 5 kcal for every year of age, which reflects the gradual loss of muscle and organ mass over time. For the same body size, that adds up to 50 kcal a decade:
| Age | Woman, 60 kg, 160 cm | Man, 75 kg, 175 cm |
|---|---|---|
| 25 | 1,314 | 1,724 |
| 35 | 1,264 | 1,674 |
| 45 | 1,214 | 1,624 |
| 55 | 1,164 | 1,574 |
Much of that decline can be slowed. Strength training preserves muscle, and staying active keeps your total daily burn much higher than BMR alone suggests.
BMR vs RMR vs TDEE
- BMR — measured in strict lab conditions: after sleep, fasting, lying still in a warm room.
- RMR (resting metabolic rate) — measured under looser conditions and usually slightly higher. Online tools, including this one, estimate something between the two; the terms are often used interchangeably.
- TDEE — BMR plus digestion, daily movement and exercise. This is the number to base eating targets on.
Can you raise your BMR?
A little. Muscle tissue burns more energy than fat, so building muscle nudges BMR up — but the effect is modest, roughly 10–15 calories a day per kilogram of muscle at rest, not hundreds. Supplements, “metabolism-boosting” foods and detox teas have no meaningful effect.
The bigger wins are outside BMR: more daily steps, regular strength training and enough protein. They raise your total daily burn and help you keep muscle while losing fat. Start with progressive overload.
Worked example: Rahul
Rahul is a 25-year-old man, 75 kg and 175 cm.
- 10 × 75 = 750
- 6.25 × 175 = 1,093.75
- 5 × 25 = 125
- 750 + 1,093.75 − 125 + 5 = 1,724 kcal/day
If Rahul knew he had 15% body fat, Katch–McArdle would give 370 + 21.6 × 63.75 kg lean mass = about 1,747 kcal — very close. With his gym routine (moderately active), his maintenance would be about 2,672 kcal.
How this calculator works
This calculator uses the Mifflin–St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years), then +5 for men or −161 for women. The result is rounded to the nearest calorie.
Only lab testing (indirect calorimetry) measures BMR directly. Any equation can be off for an individual, especially for very muscular people, people with obesity, older adults and some thyroid or hormonal conditions.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990.
- 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.
- ICMR–National Institute of Nutrition. Nutrient Requirements for Indians (2020): recommendation on energy requirement.
Frequently asked questions
Straight answers about this calculator. Educational only — not medical advice.
It depends on your size, age and sex. Many adult women fall somewhere around 1,200–1,500 kcal a day and many adult men around 1,500–1,900 kcal, but larger and more muscular people can be well above that.
Usually not. Your BMR is below your real daily burn. Base fat-loss targets on TDEE instead — a 10–20% deficit from maintenance is a better starting point than eating at BMR.
BMR scales with body size and muscle. Someone taller, heavier or more muscular will usually have a higher BMR. Age and sex also play a role.
Differences between similar people are usually smaller than expected. More often, the gap comes from daily movement and under-counted food. Thyroid problems can lower metabolism — speak to a doctor if you have symptoms.
Yes, somewhat. A smaller body burns less, and your body adapts a little to eating less. Keeping protein high and continuing strength training helps limit the drop.
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This calculator provides an estimate and isn't a substitute for individualised medical or dietary advice. Read our medical disclaimer and editorial policy.