Health & fitness
BMR Calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to keep you alive at complete rest — powering your heart, lungs, brain and other organs while you do absolutely nothing. Enter your sex, age, height and weight in U.S. customary units (feet, inches and pounds) or metric to estimate that baseline using the Mifflin-St Jeor equation, the formula most dietitians and the American Council on Exercise reach for today because it tracks real-world metabolism more closely than the older Harris-Benedict numbers. Your BMR is the foundation for figuring total daily calorie needs, so it's the first step before planning meals or a weight goal. The calculator updates as you type, runs entirely in your browser, and shows the exact formula below. This is general information only, not medical advice — talk to a licensed professional before making health decisions.
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BMR is an estimate of resting energy needs, not a diagnosis. Actual metabolism varies with body composition, genetics and health.
How the BMR calculator works
This tool uses the Mifflin-St Jeor equation, published in 1990 and now the most widely recommended formula for estimating resting energy needs. It takes your weight in kilograms, height in centimeters and age in years, then adds a constant that differs by sex. Imperial inputs (feet, inches and pounds) are converted to metric first, so the result is identical either way.
Mifflin-St Jeor equation
Men: BMR = 10W + 6.25H − 5A + 5 Women: BMR = 10W + 6.25H − 5A − 161where: W = weight in kilograms (lb ÷ 2.2046) H = height in centimeters (in × 2.54) A = age in years result is calories per day at complete rest
The only difference between the male and female formulas is the final constant: +5 for men and −161 for women, which reflects average differences in lean body mass.
Notes & assumptions
- Designed for adults; it is less accurate for children, the elderly, or people with very high or low body fat.
- BMR measures resting needs only — it does not include the calories you burn moving, exercising or digesting food.
- Calculations are for general information only and are not medical advice — consult a healthcare professional before relying on them.
Worked example
Say you're a 30-year-old man in Texas who stands 5 ft 9 in tall and weighs 160 lb. First convert: 5 ft 9 in is 69 inches × 2.54 = 175.26 cm, and 160 lb ÷ 2.2046 = 72.57 kg. Now plug into the men's formula: BMR = (10 × 72.57) + (6.25 × 175.26) − (5 × 30) + 5 = 725.7 + 1095.4 − 150 + 5, which gives a BMR of about 1,676 calories per day. That's roughly the energy this person would burn lying in bed all day, doing nothing. A 30-year-old woman of the same height and weight would use the −161 constant instead of +5, landing near 1,510 calories per day. Change any input above and every number recalculates instantly.
Frequently asked questions
What is BMR and why does it matter?
BMR, or Basal Metabolic Rate, is the number of calories your body needs to perform its most basic life-sustaining functions at complete rest — breathing, circulating blood, regulating temperature and keeping your organs running. It typically accounts for 60 to 70 percent of the calories you burn in a day. Knowing your BMR matters because it's the starting point for estimating your total daily calorie needs, which in turn guides any plan to lose, maintain or gain weight.
What's the difference between BMR and TDEE?
BMR is the calories you burn at rest, doing nothing. TDEE — Total Daily Energy Expenditure — is your BMR multiplied by an activity factor that accounts for movement, exercise and the energy used to digest food. In other words, BMR is the floor and TDEE is the realistic total. To get your TDEE, multiply your BMR by a number from about 1.2 (sedentary) up to 1.9 (very active), which our TDEE calculator does for you.
Why does this use the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation, published in 1990, is considered the most accurate of the common BMR formulas for the general population. A 2005 review by the American Dietetic Association found it predicted resting energy needs more reliably than the older Harris-Benedict and Owen equations. It relies only on sex, age, height and weight, which makes it easy to use without body-fat testing while still being reasonably accurate for most adults.
Can I increase my BMR?
To a degree. Because muscle tissue burns more calories at rest than fat, building lean muscle through resistance training can modestly raise your BMR over time. Staying active, getting enough protein and avoiding very-low-calorie crash diets — which can lower your metabolism — also help. That said, a large share of your BMR is set by factors you can't change, such as age, sex, height and genetics, so expect gradual rather than dramatic shifts.
Is this BMR estimate accurate for me?
For most healthy adults the Mifflin-St Jeor estimate lands within a few hundred calories of measured values, which is good enough for planning. It is less reliable at the extremes — very muscular athletes, people with obesity, the very old or very young — because it can't see body composition. Treat the number as a reasonable starting estimate, not a precise medical measurement, and consult a registered dietitian or doctor for a personalized assessment.