How to Calculate Your BMR and Why It Matters

What Is BMR?

BMR stands for Basal Metabolic Rate — the number of calories your body burns at complete rest just to keep you alive. This includes breathing, circulating blood, and maintaining body temperature.

Think of it as the energy cost of simply existing. Even if you stayed in bed all day, your body would still need this many calories.

The Mifflin-St Jeor Equation

The most widely recommended formula for calculating BMR is the Mifflin-St Jeor equation, published in 1990. It is considered more accurate than the older Harris-Benedict equation.

For men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5

For women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161

Example

A 30-year-old man weighing 80 kg and standing 180 cm tall:

BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1125 − 150 + 5 = 1780 kcal/day

From BMR to TDEE

BMR alone doesn't tell you how many calories you need each day. You also need to factor in physical activity. This gives you your TDEE (Total Daily Energy Expenditure).

TDEE = BMR × Activity Factor

Activity Level	Factor	Description
Sedentary	1.2	Little or no exercise
Lightly active	1.375	1–3 days/week
Moderately active	1.55	3–5 days/week
Very active	1.725	6–7 days/week
Extra active	1.9	2× daily or physical job

Using the example above with moderate activity: 1780 × 1.55 = 2759 kcal/day.

How to Use Your BMR

Once you know your TDEE, you can set a calorie target based on your goal:

• Lose weight: Eat 300–500 kcal below TDEE
• Maintain weight: Eat at TDEE
• Gain muscle: Eat 200–400 kcal above TDEE

Try It Yourself

Use our calorie calculator to get your BMR and TDEE instantly. Then check your macronutrient breakdown to split those calories into protein, fat, and carbs.