What is basal metabolic rate (BMR)?
Your BMR is the energy your body burns just to stay alive while resting: breathing, pumping blood, keeping organs working, regulating temperature and repairing cells. For most people it is the biggest share of daily calorie use, with the rest going to movement and to digesting food. This calculator estimates it from your age, sex, height and weight, and shows what that means for your daily calorie needs.
BMR is measured under strict lab conditions, so online tools like this one give an estimate. Use the number as a starting point, then adjust using real-world results over a few weeks.
BMR formulas used
Sources: Mifflin et al., original adult resting-energy study; NIDDK guidance on adult energy planning; Roza and Shizgal, revised Harris-Benedict; research comparison including Katch-McArdle.
| Formula | Equation (W = kg, H = cm, A = years, F = body fat %) |
|---|
| Mifflin-St Jeor | Men: 10W + 6.25H − 5A + 5 · Women: 10W + 6.25H − 5A − 161 |
| Revised Harris-Benedict | Men: 13.397W + 4.799H − 5.677A + 88.362 · Women: 9.247W + 3.098H − 4.330A + 447.593 |
| Katch-McArdle | 370 + 21.6 × (1 − F/100) × W |
The default Mifflin-St Jeor equation predicts resting energy expenditure from adult measurements. The other equations offer comparisons, not a diagnosis; body-fat measurement error affects Katch-McArdle.
What affects your BMR?
- Muscle mass: muscle burns more at rest than fat, so more lean mass means a higher BMR.
- Age: BMR tends to decline gradually with age, partly through loss of muscle.
- Size and sex: larger bodies burn more, and men on average burn more than women of the same weight.
- Genetics and health: thyroid function, hormones and illness all play a part.
- Diet history: long, severe calorie restriction can lower metabolic rate.
- Temperature: very cold or hot environments increase energy use.
BMR is not the same as resting metabolic rate (RMR), which is measured under looser conditions, or TDEE, which adds activity. The numbers are usually close enough that the terms are often used interchangeably.
BMR calculator FAQ
What is BMR?
BMR (basal metabolic rate) is the energy your body needs at complete rest to keep vital functions running, such as breathing, circulation and cell repair. It is usually the largest part of the calories you burn in a day.
Which BMR formula is the most accurate?
No equation is most accurate for everyone. Mifflin-St Jeor is the default here, while the other equations provide comparisons. Only measured energy expenditure and individual assessment can evaluate your needs directly.
What is the difference between BMR and TDEE?
BMR is what you burn at rest. TDEE (total daily energy expenditure) adds the calories used for movement, exercise and digesting food. It is estimated by multiplying BMR by an activity factor, as shown in the activity table.
Can I eat less than my BMR to lose weight?
Eating far below your BMR for long periods is not recommended, because it can cause fatigue, muscle loss and nutrient shortfalls. A moderate deficit below your daily needs is the usual approach. Talk to a doctor or dietitian before using very low targets.
Does building muscle raise my BMR?
Yes, slightly. Muscle burns more energy at rest than fat, so more lean mass raises BMR over time. Strength training is the most effective way to build it.
Important
For adults aged 18–100. This tool is not intended for pregnancy, breastfeeding or children. The sex categories reflect the published equations; they do not account for individual hormone treatment, body composition or medical conditions. No measurements are stored or added to your address automatically.
Links containing measurements reveal them to anyone with the link. Values after # stay outside the page request; older links using ? may appear in hosting logs.
This calculator gives general estimates for adults and is not medical advice. If you are pregnant or breastfeeding, under 18, managing a health condition or planning significant changes to your diet, talk to a doctor or registered dietitian. Last updated October 2026.