BMR Calculator

BMR stands for Basal Metabolic Rate, the number of calories your body burns at complete rest just to stay alive. Even if you spent an entire day lying in bed without moving, your body would still need energy to keep your heart beating, your lungs breathing, your brain thinking, your organs functioning, and your body temperature stable. That baseline energy requirement is your BMR, and for most adults it accounts for roughly 60 to 70 percent of all the calories they burn in a day.

Knowing your BMR is the starting point for almost any nutrition plan. It tells you the absolute minimum your body needs before you add the calories burned through walking, working, exercising, and digesting food. Once you know that number you can build a realistic daily calorie target, whether your goal is fat loss, muscle gain, or simply maintaining your current weight without guessing. Eating consistently below your BMR is generally a bad idea because it can slow metabolism, reduce energy, and cost you muscle rather than fat.

The calculator uses the Mifflin St Jeor equation, which is the formula most dietitians and sports scientists consider the most accurate general purpose estimate for healthy adults. For men the formula is 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age in years plus 5. For women the same formula is used but 161 is subtracted at the end instead of adding 5. The output is your resting calorie burn in a 24 hour period.

Your BMR is then multiplied by an activity factor to produce your Total Daily Energy Expenditure, or TDEE. Sedentary multiplies by 1.2, lightly active by 1.375, moderately active by 1.55, very active by 1.725, and extremely active by 1.9. TDEE is the number of calories you need to maintain your current weight. Eating roughly 500 calories below it usually produces steady fat loss of about half a kilogram per week, while eating a modest surplus above it supports muscle gain when combined with resistance training.