Understanding BMR

BMR represents the minimum number of calories your body needs to maintain basic functions like breathing, circulation, and cell production while at complete rest. It is a screening level estimate and can vary across individuals.

BMR formulas

Different formulas exist. This calculator includes:

• Mifflin-St Jeor (commonly recommended):
  • Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) + 5
  • Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) - 161
• Original Harris-Benedict:
  • Men: BMR = 66.5 + (13.75 × weight(kg)) + (5.003 × height(cm)) - (6.755 × age)
  • Women: BMR = 655.1 + (9.563 × weight(kg)) + (1.850 × height(cm)) - (4.676 × age)
• Revised Harris-Benedict:
  • Men: BMR = 88.362 + (13.397 × weight(kg)) + (4.799 × height(cm)) - (5.677 × age)
  • Women: BMR = 447.593 + (9.247 × weight(kg)) + (3.098 × height(cm)) - (4.330 × age)
• Katch-McArdle (needs body fat percentage):
  • BMR = 370 + (21.6 × Lean Body Mass(kg))
  • Lean Body Mass = Weight × (100 - Body Fat %) / 100

Factors affecting BMR

• Body composition: more muscle mass generally increases BMR.
• Age: BMR often decreases with age.
• Gender: equations differ due to average body composition differences.
• Other: genetics, hormones, pregnancy, and temperature can influence energy use.

Activity level multipliers

To estimate daily calories (often called TDEE), multiply BMR by an activity factor.

• Sedentary: BMR × 1.2
• Lightly active: BMR × 1.375
• Moderately active: BMR × 1.55
• Very active: BMR × 1.725
• Extra active: BMR × 1.9

Using BMR for weight management

• Weight loss: aim for a calorie deficit below your daily estimate.
• Weight gain: aim for a calorie surplus above your daily estimate.
• Maintenance: match intake to a realistic activity level estimate and adjust over time.

This calculator provides estimates based on standard formulas. Individual metabolic rates may differ.

References

Wikipedia: Basal metabolic rate