BMR Calculator
Free BMR calculator to find how many calories your body burns at rest using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas.
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Discover Your Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, and cell production. Understanding your BMR is the foundation for any weight management or nutrition plan. Our calculator uses multiple scientifically-validated formulas to give you the most accurate estimate.
What Is BMR?
Basal Metabolic Rate (BMR) represents the minimum calories your body requires at complete rest—as if you stayed in bed all day. It accounts for 60-75% of your total daily calorie expenditure. Factors affecting BMR include age, sex, weight, height, muscle mass, and genetics. BMR decreases with age and increases with muscle mass.
Mifflin-St Jeor Equation (Most Accurate)
Men: BMR = (10 × weight) + (6.25 × height) - (5 × age) + 5How to Calculate BMR
Enter your weight (kg or lbs)
Enter your height (cm or inches)
Enter your age
Select your biological sex
Choose a formula (Mifflin-St Jeor recommended for most)
View your BMR and activity-adjusted calorie needs
Common Use Cases
Weight Loss Planning
Establish your baseline calorie needs to create an effective and safe calorie deficit.
Fitness & Bodybuilding
Determine minimum calorie intake to support muscle building without excessive fat gain.
Medical Nutrition
Healthcare professionals use BMR to calculate nutritional needs for patients.
Understanding Metabolism
Learn how your body uses energy at rest and how factors like age and muscle affect it.
Why Calculate Your BMR?
Set an accurate calorie baseline
BMR is 60–75% of the calories you burn daily — it anchors every deficit or surplus you plan.
Compare three validated formulas
See how Mifflin-St Jeor, revised Harris-Benedict, and Katch-McArdle differ for your stats, then pick the one that fits.
Turn BMR into daily targets
Each result is multiplied by five activity factors (1.2–1.9) so you get an actionable calories/day range, not just one number.
Avoid under-eating and metabolic slowdown
Eating below BMR for long periods can blunt your metabolism; knowing the floor keeps deficits safe.
Account for muscle with body fat %
Katch-McArdle uses lean body mass, so leaner or more muscular bodies get a more precise estimate than height-weight formulas.
Frequently Asked Questions
Mifflin-St Jeor is most accurate for most people and is recommended by the Academy of Nutrition and Dietetics. Use Katch-McArdle if you know your body fat percentage, as it accounts for muscle mass.
BMR is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) includes BMR plus calories burned through activity. TDEE = BMR × Activity Multiplier. Use TDEE for daily calorie goals.
Muscle tissue is metabolically active—it burns calories even at rest. More muscle = higher BMR. This is why strength training can help with weight management by increasing your baseline calorie burn.
Yes, BMR decreases about 1-2% per decade after age 20, mainly due to muscle loss and hormonal changes. Regular exercise, especially strength training, can help minimize this decline.
These formulas estimate BMR within about 10% accuracy for most people. For precise measurement, you'd need indirect calorimetry testing. Calculators are useful starting points—adjust based on real-world results.