Basal Metabolic Rate Calculator (BMR)
Calculate your basal metabolic rate with Harris-Benedict, Mifflin-St Jeor and Katch-McArdle. Formula comparison.
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Everything you need to know about Basal Metabolic Rate (BMR)
Why should you calculate your BMR?
Your basal metabolic rate accounts for 60 to 75% of your total daily energy expenditure. Knowing it is the essential first step to building a realistic nutrition plan, whether your goal is weight loss, muscle gain, or maintenance.
Unlike one-size-fits-all estimates (2,000 kcal for everyone), BMR varies significantly based on sex, age, height, weight, and body composition. A 90 kg man and a 55 kg woman have vastly different baseline needs.
Our calculator compares three scientifically validated formulas (revised Harris-Benedict, Mifflin-St Jeor, Katch-McArdle) to give you a reliable range rather than a single number. This cross-referencing approach provides a more robust estimate.
Who uses a BMR calculator?
- People trying to lose weight
- Knowing your BMR helps set a reasonable calorie deficit (300-500 kcal below TDEE) without dropping below your metabolic threshold, which prevents muscle loss and yo-yo dieting.
- Athletes and strength trainers
- During bulking or cutting phases, BMR serves as the foundation for calculating TDEE with the right activity multiplier and adjusting macronutrient ratios accordingly.
- Dietitians and nutritionists
- Healthcare professionals use these formulas daily to create personalized meal plans. Comparing multiple formulas strengthens the accuracy of the initial energy assessment.
- Sedentary individuals looking to improve their health
- Even without athletic goals, understanding your baseline caloric needs helps make informed food choices and prevent the gradual weight gain that comes with aging.
How does the calculation work?
Enter your biometric data: sex, age, weight in kilograms, and height in centimeters. If you know your body fat percentage, add it to unlock the Katch-McArdle formula.
The calculator simultaneously applies three scientific formulas. Harris-Benedict (revised 1984) and Mifflin-St Jeor (1990) use total body weight, while Katch-McArdle relies on lean body mass for better accuracy in muscular or high-adiposity individuals.
You get an average BMR along with a per-formula breakdown and visual comparison. Then multiply the result by your activity factor (1.2 to 1.9) to obtain your TDEE (Total Daily Energy Expenditure).
Frequently asked questions about BMR
- What is the difference between BMR and TDEE?
- BMR (Basal Metabolic Rate) is the energy expended at complete rest over 24 hours. TDEE (Total Daily Energy Expenditure) additionally includes physical activity, the thermic effect of food, and NEAT (non-exercise activity thermogenesis). TDEE is typically 1.2 to 1.9 times higher than BMR.
- Which BMR formula is the most reliable?
- The American Dietetic Association recommends Mifflin-St Jeor as the most accurate formula for the general population. However, if you know your body fat percentage, Katch-McArdle is more precise because it accounts for actual body composition.
- Can my basal metabolic rate change over time?
- Yes. BMR naturally decreases by about 1 to 2% per decade after age 20, mainly due to loss of muscle mass. Strength training, quality sleep, and a protein-rich diet help maintain a higher metabolism.
- Should I eat below my BMR to lose weight?
- No, eating below your BMR for extended periods is not recommended. It can slow your metabolism, cause nutrient deficiencies, and lead to muscle loss. A moderate deficit (300-500 kcal) below your TDEE is more effective and sustainable.
- Why do the three formulas give different results?
- Each formula was developed using different populations and at different times. Harris-Benedict (1919, revised 1984) tends to slightly overestimate. Mifflin-St Jeor (1990) corrects this bias. Katch-McArdle uses lean mass instead of total weight, making it more accurate for atypical profiles (very muscular or significantly overweight individuals).