BMR Formula Explained

This reference explains the BMR formula used by our free BMR Calculator. Use it to understand variables, units, and common mistakes before you calculate.

The formula

BMR (Mifflin-St Jeor) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s

Variables and units

• weight — Body weight (kg)
• height — Height (cm)
• age — Age in years (years)
• s — Sex constant (+5 male, −161 female) (kcal)

Worked example

Inputs: Male, 80 kg, 180 cm, 35 years

1. BMR = 10×80 + 6.25×180 − 5×35 + 5
2. BMR = 800 + 1125 − 175 + 5 = 1,755 kcal

Result: BMR ≈ 1,755 kcal/day

When to use this formula

Use this formula when you need a quick bmr estimate with values you already know. Our BMR Calculator applies the same relationship automatically so you can verify handwritten work.

Common mistakes

• Using BMR as total daily calories (must multiply by activity factor for TDEE)
• Using imperial units in the Mifflin formula without converting
• Comparing BMR across different formulas without consistency

Frequently asked questions