Basal Metabolic Rate Calculator

The basal metabolic rate (BMR) is the number of calories your body requires to maintain essential functions such as breathing, circulation, and temperature regulation while at rest. This calculator uses the Mifflin-St Jeor formula, which takes into account your height, weight, age, and sex to provide a personalized baseline energy estimate.

Why BMR matters for daily nutrition planning

Understanding your BMR helps you determine how many calories are consumed even before you add exercise, work, or daily chores. It is the foundation for adjusting intake for weight loss, gain, or maintenance, and it can signal when calorie targets are too low for long-term health.

Example: A 34-year-old man who weighs 82 kg and is 180 cm tall has a BMR ≈ 1,770 kcal/day using the male Mifflin-St Jeor calculation. With moderate activity (multiplier 1.55) his maintenance calories rise to about 2,744 kcal/day, which shows how activity multiplies that resting requirement.

Example: A 28-year-old woman weighing 64 kg at 168 cm tall has a BMR ≈ 1,389 kcal/day. If she leads a lightly active lifestyle (multiplier 1.375) her total daily energy expenditure becomes 1,911 kcal/day, giving a realistic target for balanced fueling.

Enter your measurements

Interpreting the results

The BMR value represents how many calories your body needs at rest; it excludes digestion and movement. The higher activity multiplier adjusts that figure to estimate your total daily energy expenditure (TDEE), which you can use to set realistic eating goals. Use lower-than-maintenance calories for gradual loss, maintenance calories to stay stable, and slightly higher for building lean mass.

Remember, BMR shifts with muscle mass changes, aging, and hormonal fluctuations, so revisit the calculator every few months or after significant body composition changes to keep your nutritional strategy accurate.