Free BMI and Calorie Calculator

BMI compares your weight to your height to give a quick screening estimate of whether your weight falls in a typical range. It is a useful starting point, but it does not account for muscle mass, bone density, or where fat is stored on your body, so an athlete with a lot of muscle can show a higher BMI despite being lean.

Your BMR is the number of calories your body burns just to stay alive: breathing, circulating blood, and keeping your organs running, if you stayed in bed all day. We calculate it using the Mifflin-St Jeor equation, one of the most accurate formulas available for estimating this.

This is your BMR multiplied by your activity level, giving an estimate of how many calories you burn in an average day including exercise and daily movement. It is also called your maintenance calories: eating around this amount should keep your weight roughly stable.

To lose weight you need to eat fewer calories than you burn, a deficit. To gain weight you need to eat more, a surplus. We apply a moderate, sustainable adjustment to your maintenance calories based on the goal you selected, rather than an extreme one that is hard to stick to.

Protein helps preserve or build muscle while you are losing weight, gaining weight, or maintaining. Your target is based on your body weight and your goal, set higher when cutting calories to help protect your muscle mass.

Using the rule of thumb that roughly 7,700 kcal equals about 1 kg of body fat, we estimate how quickly you could reach your goal at your current calorie target. Actual results vary from person to person.