About the BMR Calculator
Your basal metabolic rate (BMR) is the energy your body uses in 24 hours just to stay alive at complete rest — breathing, circulating blood, keeping organs working and maintaining body temperature. For most people it makes up roughly 60–70% of the calories they burn in a day, so it is the foundation of any calorie or weight plan.
This calculator gives your BMR using three well-known prediction equations side by side. Mifflin-St Jeor is the default because it is the most accurate for most adults; the revised Harris-Benedict equation is the long-standing classic; and Katch-McArdle uses lean body mass, which suits people who know their body fat percentage, particularly lean or muscular people.
It also multiplies your BMR by standard activity factors to estimate total daily energy expenditure (TDEE), the number to eat at to maintain your weight. All three equations are estimates for healthy adults; individual metabolism can differ by 10% or more.
With the default inputs, the basal metabolic rate is 1,712 kcal/day. Change any value above to recalculate instantly.
How to use the bmr calculator
- 1Pick a formula — Mifflin-St Jeor unless you know your body fat percentage.
- 2Select your sex and enter your age.
- 3Enter your height and weight in US or metric units.
- 4For Katch-McArdle, enter your body fat percentage.
- 5Choose your activity level to see daily maintenance calories.
Formula and method
Mifflin-St Jeor (1990) predicts resting energy expenditure from weight, height, age and sex and is generally the most accurate of the common equations for healthy adults. The revised Harris-Benedict equation (Roza and Shizgal, 1984) updates the original 1919 formula and tends to give slightly higher results. Katch-McArdle ignores sex and age and instead uses lean body mass (weight × (1 − body fat %)), so it depends on a good body fat estimate.
Daily calories (TDEE) are BMR multiplied by an activity factor from 1.2 for sedentary people to 1.9 for very hard daily training. These multipliers are broad averages, so treat the result as a starting point and adjust after a few weeks of tracking your weight.
- W
- Weight in kilograms
- H
- Height in centimetres
- A
- Age in years
- LBM
- Lean body mass in kg = W × (1 − body fat % ÷ 100)
Worked examples
35-year-old man, 5 ft 10 in, 170 lb, moderately active
In metric this man is 77.1 kg and 177.8 cm. Mifflin-St Jeor gives 10 × 77.1 + 6.25 × 177.8 − 5 × 35 + 5 ≈ 1,712 kcal/day. Multiplying by 1.55 for moderate activity gives about 2,654 kcal/day to maintain his weight.
28-year-old woman, 165 cm, 60 kg, sedentary
Mifflin-St Jeor: 10 × 60 + 6.25 × 165 − 5 × 28 − 161 = 1,330 kcal/day. The revised Harris-Benedict equation gives about 1,392. With a sedentary multiplier of 1.2 her maintenance intake is roughly 1,596 kcal/day.
Katch-McArdle for a lean lifter: 90 kg at 12% body fat
Lean body mass is 90 × 0.88 = 79.2 kg, so Katch-McArdle gives 370 + 21.6 × 79.2 = 2,081 kcal/day. At a very active 1.725 multiplier, maintenance is around 3,589 kcal/day.
Frequently asked questions
What is the difference between BMR and RMR?+
BMR is measured under strict conditions — fully rested, fasted and at a neutral temperature — while resting metabolic rate (RMR) is measured under looser conditions and usually comes out a few percent higher. Prediction equations like Mifflin-St Jeor are often used interchangeably for both.
Which BMR formula is most accurate?+
For most healthy adults, Mifflin-St Jeor predicts measured resting metabolism most closely, typically within about 10%. Katch-McArdle can be better for very lean or muscular people if their body fat percentage is known accurately.
Should I eat my BMR calories to lose weight?+
Usually not. BMR is what you burn lying still all day; your real daily burn (TDEE) is higher. A common approach is to eat around 300–500 kcal below TDEE, not at or below BMR, to lose weight steadily without excessive hunger or muscle loss.
Why does BMR go down with age?+
Resting energy use falls with age mainly because people tend to lose muscle mass and organ metabolic rate declines slightly. Strength training helps preserve muscle, which is one of the few ways to limit that decline.
Is a higher BMR better?+
A higher BMR simply means you burn more energy at rest, usually because you are larger or carry more muscle. It makes weight maintenance easier at a given intake but is not in itself a marker of better health.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.