BMR Calculator
This BMR calculator uses the Mifflin–St Jeor equation to estimate your basal metabolic rate — the calories your body burns at complete rest. Enter your age, sex, height, and weight to get your number, with the Harris–Benedict estimate alongside it.
What basal metabolic rate is
Basal metabolic rate (BMR) is the energy your body uses at complete rest to keep essential functions running — breathing, circulation, cell repair, and brain activity. It's the single biggest part of most people's daily energy use and the baseline you build a calorie target on.
The Mifflin–St Jeor equation
Using kilograms, centimetres, and years:
Men: BMR = 10·kg + 6.25·cm − 5·age + 5
Women: BMR = 10·kg + 6.25·cm − 5·age − 161
Source: Mifflin MD, St Jeor ST, et al. (1990).
Worked example
A 30-year-old man, 170 lb (77.1 kg) and 5'10" (177.8 cm): BMR = 10·77.1 + 6.25·177.8 − 5·30 + 5 = 1,737 kcal/day. The revised Harris–Benedict equation gives ~1,804 kcal/day for the same person.
BMR vs TDEE: activity multipliers
| Activity level | Multiplier | Typical week |
|---|---|---|
| Sedentary | ×1.2 | little or no exercise |
| Light | ×1.375 | exercise 1–3 days/week |
| Moderate | ×1.55 | exercise 3–5 days/week |
| Very active | ×1.725 | exercise 6–7 days/week |
| Athlete | ×1.9 | hard daily training / physical job |
Mifflin–St Jeor vs Harris–Benedict
The Harris–Benedict equation was the long-time standard but tends to overestimate BMR slightly for modern body compositions. Mifflin–St Jeor is now a common default. If you know your body-fat percentage, the Katch–McArdle formula can be useful for very lean or very muscular people.
Frequently asked questions
What is BMR?
- The calories your body burns at complete rest to keep basic functions running.
BMR vs TDEE — what's the difference?
- TDEE is BMR multiplied by an activity factor; it's your total daily burn including movement and exercise.
Which BMR formula is most accurate?
- Mifflin–St Jeor is a widely used modern estimate for the general population.
How do I use BMR to lose weight?
- Estimate TDEE from BMR, then compare that with your intake; your actual needs vary by activity and individual factors.
Does BMR decrease with age?
- The equation includes age, and resting energy needs commonly decline over time as body composition changes.
Disclaimer. BMR is an estimate for healthy adults and not a medical or nutrition prescription. Actual energy needs vary.