What Is BMR? Understanding Your Metabolism

Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to stay alive — powering your heart, lungs, brain, and cell repair — while completely at rest. It doesn’t include any calories used for movement, digestion, or exercise.

Why BMR Matters

BMR typically accounts for 60–75% of total daily calorie burn for most people, making it the single biggest factor in your overall energy needs. Understanding your BMR is the foundation for setting realistic calorie targets, whether your goal is weight loss, maintenance, or muscle gain.

What Affects Your BMR

Muscle mass, age, sex, genetics, and body size all influence BMR. More muscle mass raises BMR because muscle tissue burns more calories at rest than fat tissue. BMR also tends to decline gradually with age, largely due to natural muscle loss over time.

How to Find Your BMR

The most common estimation method is the Mifflin-St Jeor equation, which uses your weight, height, age, and sex. You can get an instant estimate with our BMR Calculator, or go deeper with goal-based planning using BMR Analysis.

Source: NIH — Estimated Energy Requirements.