TDEE Formula Explained

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

The formula

TDEE = BMR × activity multiplier (1.2 sedentary → 1.9 extra active)

Variables and units

• BMR — Basal metabolic rate from Mifflin-St Jeor or Harris-Benedict (kcal/day)
• activity multiplier — Factor from 1.2 (sedentary) to 1.9 (extra active) (dimensionless)

Worked example

Inputs: BMR 1,650 kcal, moderately active (multiplier 1.55)

1. Multiply BMR by activity factor: 1,650 × 1.55 = 2,557.5

Result: TDEE ≈ 2,558 kcal/day

When to use this formula

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

Common mistakes

• Using BMR alone as daily calorie target
• Overestimating activity level (most people are sedentary to lightly active)
• Forgetting that TDEE changes with weight loss

Frequently asked questions