BMI Calculator

BMI (Body Mass Index) is a number derived from your weight and height. The metric formula is: BMI = weight in kilograms divided by height in meters squared. For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9. It is used as a general screening indicator for weight categories.

The World Health Organization defines four adult BMI categories: Underweight (below 18.5), Normal weight (18.5 to 24.9), Overweight (25.0 to 29.9), and Obese (30.0 and above). These ranges apply to adults aged 18 and older. Children and teenagers use age- and sex-specific charts.

BMI is a useful population-level screening tool, but it has limitations for individuals. It does not distinguish between fat mass and muscle mass, so athletes with high muscle mass may be classified as overweight even when they are healthy. It also does not account for fat distribution, age, sex, or ethnicity. Always interpret BMI alongside other health indicators.

The imperial formula is: BMI = 703 × weight (lb) ÷ height² (in). For example, a person weighing 154 lb and standing 69 inches tall has a BMI of 703 × 154 ÷ (69 × 69) = 22.7. Select 'Imperial' on this calculator and it will apply the correct formula automatically.

A BMI between 18.5 and 24.9 is generally considered the normal or healthy weight range for adults. However, 'healthy weight' is a complex concept. Factors such as fitness level, diet, blood pressure, and family history are equally or more important than BMI alone. Use BMI as a starting point for a conversation with your doctor, not as a definitive health verdict.