BMR Calculator

The BMR (Basal Metabolic Rate) Calculator estimates the number of calories your body burns at complete rest — just to maintain basic life functions like breathing, circulation, cell production, and temperature regulation. BMR accounts for 60–70% of your total daily calorie expenditure.

Your BMR is the minimum energy your body needs to survive if you did absolutely nothing all day — not even eating or thinking. It's influenced by age, sex, height, weight, body composition, and genetics. BMR decreases with age (about 1–2% per decade after age 20) and is generally higher in men due to greater muscle mass. Understanding your BMR is the foundation for any weight management plan.

How the Formula Works

Mifflin-St Jeor (most accurate): Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 5. Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161.

  • Mifflin-St Jeor: Considered the most accurate for most people
  • Harris-Benedict (original): Men = 66.5 + 13.75×wt + 5.003×ht − 6.75×age
  • Harris-Benedict (revised): Men = 88.362 + 13.397×wt + 4.799×ht − 5.677×age
  • Katch-McArdle: BMR = 370 + 21.6 × Lean Body Mass (kg) — requires body fat % input

How to Use This Calculator

  1. Enter your age, sex, weight, and height
  2. View your estimated BMR in calories per day
  3. Multiply by your activity factor to get TDEE (Total Daily Energy Expenditure)

Tips & Best Practices

  • Use BMR as a baseline — never eat below your BMR for extended periods
  • Muscle mass is the biggest controllable factor affecting BMR — strength training helps
  • BMR decreases with age; adjust your calorie intake accordingly
  • The Mifflin-St Jeor equation is considered the most accurate for most people by the Academy of Nutrition and Dietetics

Important Limitations

  • All BMR formulas are estimates — individual variation can be 5–15%
  • Does not account for body composition unless using Katch-McArdle formula
  • Metabolic conditions (hypothyroidism, etc.) can significantly affect actual BMR
  • Extreme dieting can lower BMR through metabolic adaptation
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