BMR Calculator — Basal Metabolic Rate

What the BMR calculator does

Your Basal Metabolic Rate is the number of calories your body needs to stay alive at complete rest — to breathe, pump blood, regulate temperature, and run your organs. It usually accounts for 60–70% of the calories you burn each day, which makes it the foundation of any calorie plan. This calculator estimates BMR using two trusted equations and lets you compare them side by side.

How the formulas work

The Mifflin-St Jeor equation, published in 1990, is the modern standard and uses weight, height, age, and sex. The revised Harris-Benedict equation is an older but still widely cited alternative. Both predict resting energy needs; Mifflin-St Jeor is generally the more accurate for today's population, while Harris-Benedict tends to read slightly higher.

How to interpret your result

BMR alone is not your daily calorie target — you also burn energy through movement and digestion. To get your full daily needs, multiply BMR by an activity factor (use the TDEE calculator, which does this automatically). Never aim to eat below your BMR for extended periods, because chronic under-eating can slow metabolism and erode muscle.

Health recommendations

Building lean muscle through resistance training is the most reliable way to raise BMR over time. Adequate protein, sleep, and avoiding crash diets all help protect your resting metabolism. Pair this calculator with the TDEE and Calorie calculators to translate your BMR into a complete daily plan.