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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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.
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)
Establish your baseline calorie needs to create an effective and safe calorie deficit.
Determine minimum calorie intake to support muscle building without excessive fat gain.
Healthcare professionals use BMR to calculate nutritional needs for patients.
Learn how your body uses energy at rest and how factors like age and muscle affect it.
BMR is 60–75% of the calories you burn daily — it anchors every deficit or surplus you plan.
See how Mifflin-St Jeor, revised Harris-Benedict, and Katch-McArdle differ for your stats, then pick the one that fits.
Each result is multiplied by five activity factors (1.2–1.9) so you get an actionable calories/day range, not just one number.
Eating below BMR for long periods can blunt your metabolism; knowing the floor keeps deficits safe.
Katch-McArdle uses lean body mass, so leaner or more muscular bodies get a more precise estimate than height-weight formulas.
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.