BMR Calculator

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What is a BMR Calculator?

A BMR (Basal Metabolic Rate) calculator estimates how many calories your body burns each day just to stay alive at complete rest: breathing, circulating blood, regulating temperature, and maintaining organ function. It is the baseline number all calorie and diet calculations build on.

How It Works

This calculator uses the Mifflin-St Jeor equation, considered the most accurate BMR formula for most people:

Men:   (10 x kg) + (6.25 x cm) - (5 x age) + 5
Women: (10 x kg) + (6.25 x cm) - (5 x age) - 161

Example

A 35-year-old man, 180 cm tall, weighing 82 kg.

  • (10 x 82) + (6.25 x 180) - (5 x 35) + 5 = 1,892 cal/day

This is the number of calories burned at rest. Real daily needs will be higher based on activity level.

Tips

  • BMR decreases with age as muscle mass naturally declines. Strength training can help slow this effect.
  • BMR is not the same as your total daily calorie needs. Multiply by an activity factor to get TDEE (use the Calorie Calculator for this).
  • Eating below your BMR for extended periods can slow your metabolism and is generally not recommended without medical supervision.

Frequently Asked Questions

What is the difference between BMR and TDEE?

BMR is your calorie burn at complete rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for movement and exercise throughout the day. TDEE is the more practical number for planning your diet.

Why does BMR differ between men and women?

Men generally have more lean muscle mass relative to body weight, which burns more calories at rest. The Mifflin-St Jeor formula uses a constant of +5 for men and -161 for women to account for this average difference.

How accurate is BMR calculation?

Formula-based BMR estimates are accurate to within about 10% for most people. Individual variation in metabolism means the actual number could be higher or lower. The most accurate measurement requires clinical testing (indirect calorimetry).

Does BMR change when you diet?

Yes. Prolonged calorie restriction causes the body to adapt by lowering BMR, sometimes called "metabolic adaptation." This is one reason weight loss can slow or stall even when calorie intake stays the same.