BMR Calculator

Basal metabolic rate is the number of calories your body burns at complete rest to keep essential functions running, such as breathing, circulation, and cell repair. It represents the minimum energy you need each day before any activity. BMR matters because it forms the foundation of your total daily energy needs; once you know it, you can layer activity on top to estimate how much you should eat to maintain, lose, or gain weight. It typically accounts for the majority of the calories most people burn in a day.

This calculator uses the Mifflin-St Jeor equation, widely regarded as one of the more accurate formulas for estimating BMR. It combines your weight, height, age, and sex to produce an estimate, because each of these factors influences resting energy use. Muscle mass, which the formula does not measure directly, also affects metabolism, so the result is a well-supported estimate rather than an exact measurement. For a precise figure, clinical methods such as indirect calorimetry would be required.

BMR is the energy you burn at rest, while total daily energy expenditure (TDEE) adds the calories burned through movement, exercise, and digestion. TDEE is calculated by multiplying BMR by an activity factor that reflects how active you are. For everyday calorie planning, TDEE is the more practical number, but it is built directly on top of your BMR, which is why an accurate BMR estimate is the essential first step.

Resting metabolism tends to decline gradually with age, largely because people often lose muscle mass and gain fat over the years, and muscle burns more energy at rest than fat does. Hormonal changes also play a role. This is one reason maintaining the same diet over decades can lead to slow weight gain. Staying active and preserving muscle through resistance training can help counteract some of this age-related decline.

BMR is a starting point, not a target intake. To lose weight safely, you generally need a moderate calorie deficit relative to your TDEE, not your BMR. Eating only at your BMR level for an extended period is usually too restrictive and can be counterproductive. Use the BMR figure to build a realistic TDEE, then create a sensible deficit, and consider consulting a healthcare professional or dietitian for personalised guidance.