What is BMR?
BMR is the energy your body needs just to stay alive if you rested all day. For most people it makes up the largest share of daily calorie use — often around 60–70% — with the rest coming from movement, exercise and digesting food.
BMR is mostly determined by body size, lean mass, age and sex. Larger bodies and more muscle mean a higher BMR; BMR tends to decline gradually with age, partly because of changes in muscle mass.
BMR formulas used
Example (Mifflin–St Jeor): a 30-year-old woman, 165 cm, 60 kg: 600 + 1,031.25 − 150 − 161 ≈ 1,320 kcal/day.
BMR vs TDEE
BMR is not how many calories you should eat. Once you add daily movement and exercise, you burn more — this total is your Total Daily Energy Expenditure (TDEE). Eating at your BMR would usually mean a calorie deficit. Use the TDEE calculator to estimate your full daily needs.
Limitations
- Equations predict averages; your measured BMR could be 10% or more higher or lower.
- They were developed in adults and are less reliable for teenagers, older adults and people with very high or low body fat.
- Illness, some medications, thyroid conditions and pregnancy can change metabolism significantly.
Frequently asked questions
What is a normal BMR?
There is no single normal value. Many adult women have an estimated BMR of roughly 1,200–1,500 kcal/day and many men roughly 1,500–1,900 kcal/day, but it varies widely with size and body composition.
Which BMR formula is most accurate?
For healthy adults, Mifflin–St Jeor is generally considered the most reliable predictive equation. Katch–McArdle can be useful if you know your body-fat percentage accurately.
Can I increase my BMR?
Building muscle through strength training can raise BMR modestly over time. Larger short-term changes usually come from overall activity rather than BMR itself.
Should I eat my BMR in calories?
Usually not. Your total needs are higher than your BMR once activity is included. Use your TDEE as the basis for any calorie target.
Methods and 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(2):241–247.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. 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;105(5):775–789.
Content reviewed: by the FitNumbra editorial team.