Basal Metabolic Rate: What Is It and How Do You Calculate It?

What is your basal metabolism?

Your basal metabolic rate (English: Basal Metabolic Rate or abbreviated BMR) or resting metabolic rate is the amount of energy that your body burns every day if you stay in bed all day (= complete rest). This concerns all primary life processes that ensure that you stay alive, such as breathing, blood circulation, maintaining your body temperature...

The basal metabolism depends on:

• Your body weight and fat percentage
• Your height
• Your gender
• Your age

Your basal metabolism provides the majority (60-75%) of your total energy requirements.

How do I calculate my basal metabolic rate?

There are different formulas to calculate your basal metabolic rate. We limit ourselves to 2 formulas: one when your fat percentage is known, and one when you do not know it.

Katch-McArdle formula

If you know your fat percentage, you can use the following formula to calculate your basal metabolic rate:

BMR = 370 + (21.6 x your fat-free mass in kg)

You can calculate your lean body mass in kg (in English: Lean Body Mass or LBM) as follows:

LBM = your body weight in kg x (1 - your fat percentage in decimal number)

Example for someone weighing 70 kg and a body fat percentage of 10%:

LMB = 70 x (1 - 0.10) = 63 kg
BMR = 370 + (21.6 x 63) = 1730.8

Mifflin-St Jeor formula

If you do not know your exact fat percentage, you can use the Mifflin-St Jeor equation to calculate your basal metabolism:

Example for a 30 year old woman who is 165cm tall and weighs 65kg: (10 x 65) + (6 x 165) - (5 x 30) - 161 = 1329 kcal

When using this formula, it is assumed that you have a normal body fat percentage (10-20% for men, 20-30% for women). Since muscle consumes more than fat, your BMR may be slightly lower with a higher fat percentage. Although the difference is minimal (1 kg of muscle consumes about 13 calories per day compared to 4 calories for 1 kg of fat tissue) and therefore negligible.