Calories Formula Explained

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

The formula

TDEE = BMR × activity factor; targets adjust for deficit/surplus

Variables and units

• BMR — Basal metabolic rate (kcal/day)
• activity factor — Multiplier for daily activity (1.2–1.9)

Worked example

Inputs: Woman, 65 kg, 165 cm, 30 years, lightly active (1.375)

1. BMR = 10×65 + 6.25×165 − 5×30 − 161 = 1,371 kcal
2. TDEE = 1,371 × 1.375 = 1,885 kcal

Result: Daily calorie needs ≈ 1,885 kcal for maintenance

When to use this formula

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

Common mistakes

• Confusing calorie deficit calculator output with maintenance TDEE
• Ignoring liquid calories and cooking oils
• Using outdated Harris-Benedict without verifying against Mifflin-St Jeor

Frequently asked questions