Check your Body Mass Index using NHS-aligned categories. Works with both metric and imperial.
Body Mass Index (BMI) is a simple measurement that uses your height and weight to estimate whether you're a healthy weight. It's calculated by dividing your weight in kilograms by your height in metres squared. The NHS and World Health Organisation use BMI as a screening tool to identify potential weight-related health risks.
The NHS classifies BMI into four main categories. A BMI below 18.5 is considered underweight. A BMI between 18.5 and 24.9 is the healthy weight range. A BMI between 25 and 29.9 is classified as overweight, and a BMI of 30 or above is classified as obese. These categories apply to most adults, but BMI should be interpreted differently for children, pregnant women, and very muscular individuals.
While BMI is a useful screening tool, it has well-known limitations. It doesn't distinguish between muscle mass and body fat, so very muscular people may have a high BMI without being overweight. It also doesn't account for where your body stores fat — carrying weight around your middle (visceral fat) poses greater health risks than carrying it elsewhere. For a more complete picture, consider also measuring your waist circumference.
If your BMI falls outside the healthy range, it's worth speaking with your GP. They can assess your overall health in context, taking into account your age, ethnicity, muscle mass, and other risk factors. Small changes to diet and physical activity often make a meaningful difference. The NHS provides free resources and support through its Better Health programme for anyone looking to reach a healthier weight.