BMR Calculator (Harris-Benedict & Mifflin-St Jeor)
Estimate how many calories your body burns at rest with the two most widely used equations, see both formulas written out, and turn the result into maintenance calories for your activity level.
Calculate your basal metabolic rate
Your answers stay in your browser.
Two BMR estimates, side by side.
You will see your BMR by Mifflin-St Jeor and Harris-Benedict, plus maintenance calories for five activity levels.
The energy your body uses at complete rest
Basal metabolic rate (BMR) is the energy your body needs to stay alive at complete rest: breathing, circulating blood, keeping its temperature, and running your organs. For most adults it is the largest part of daily energy use, often around 60–70% of it.
BMR is not the number of calories you should eat. Daily needs, also called maintenance calories or TDEE, add what you burn through movement, exercise, and digestion. That is why the table multiplies BMR by an activity factor from 1.2 (mostly seated) to 1.9 (very hard training or physical work).
Strictly, BMR is measured lying down after an overnight fast, while resting metabolic rate (RMR) is measured under looser conditions and runs slightly higher. Online calculators, including this one, use the two terms almost interchangeably.
The Harris-Benedict and Mifflin-St Jeor formulas
W is weight in kilograms, H is height in centimeters, and A is age in years. Both return kcal per day.
Harris-Benedict (revised, 1984)
Roza and Shizgal’s revision of the original 1919 equations.
- Men
- BMR = 88.362 + (13.397 × W) + (4.799 × H) − (5.677 × A)
- Women
- BMR = 447.593 + (9.247 × W) + (3.098 × H) − (4.330 × A)
Mifflin-St Jeor (1990)
Developed from measurements of 498 healthy adults.
- Men
- BMR = (10 × W) + (6.25 × H) − (5 × A) + 5
- Women
- BMR = (10 × W) + (6.25 × H) − (5 × A) − 161
Example: a 30-year-old man who is 180 cm and 80 kg gets 1,780 kcal a day with Mifflin-St Jeor and about 1,854 kcal with Harris-Benedict.
Which BMR formula should I use?
For most adults, Mifflin-St Jeor is the better default. A 2005 systematic review found it estimated resting energy within 10% of measured values in more people than the other common equations, in both non-obese and obese adults.
Harris-Benedict is older and still widely used. It usually comes out a little higher than Mifflin-St Jeor—often around 5%, and more for heavier men—so the calculator shows it alongside rather than instead.
Neither equation knows your body composition. Very muscular people may get a closer estimate from an equation based on lean mass, such as Katch-McArdle, if they know their body-fat percentage.
An estimate, not a measurement.
- For adults 18 and older; the equations were not built for children or teenagers.
- Expect individual error of 10% or more. Only indirect calorimetry measures resting energy directly.
- Not for pregnancy, breastfeeding, or medical conditions that change metabolism, such as thyroid disorders. Ask your doctor.
- Very muscular people, such as strength athletes, often burn more at rest than these equations predict.
BMR questions, answered
What is basal metabolic rate?
Basal metabolic rate is the number of calories your body burns at complete rest to keep vital functions running, such as breathing, circulation, and temperature control. It depends mostly on body size, especially lean mass, and also on age and sex.
How is BMR calculated?
Without lab equipment, BMR is estimated with an equation from sex, age, height, and weight. Mifflin-St Jeor multiplies weight in kilograms by 10, adds 6.25 times height in centimeters, subtracts 5 times age, then adds 5 for men or subtracts 161 for women. Clinics can measure it with indirect calorimetry.
How many calories do I burn at rest?
Roughly your BMR. Many adults fall somewhere between about 1,200 and 2,200 kcal a day, depending on body size, age, and sex. For a 30-year-old woman who is 165 cm and 60 kg, Mifflin-St Jeor gives about 1,320 kcal; the calculator above gives your own estimate.
What is the difference between BMR and maintenance calories (TDEE)?
BMR is what you burn at rest. Maintenance calories, or total daily energy expenditure (TDEE), add daily movement, exercise, and digestion, and usually land between 1.2 and 1.9 times BMR. Eating at maintenance keeps weight roughly stable.
Should I eat below my BMR to lose weight?
Usually there is no need. A deficit is measured against maintenance calories, not BMR, so a moderate target often stays above BMR; the calorie and macro calculator never plans weight loss below 110% of estimated BMR. Very low-calorie diets should be supervised by a clinician.
Turn your BMR into a daily plan
The calorie and macro calculator adds your activity and goal and returns a calorie target with protein, carbs, and fat. MacroLab can then keep that estimate up to date as you log meals and weight.