BMI Calculator

For most adults in the UK, a healthy BMI falls between 18.5 and 24.9. A BMI of 25 to 29.9 is classed as overweight, and a BMI of 30 or above is classed as obese. If you have a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, NICE recommends lower thresholds: a BMI of 23 or above indicates increased health risk, and 27.5 or above indicates high risk.

BMI is calculated by dividing your weight in kilograms by your height in metres squared (kg/m²). For example, if you weigh 85 kg and are 1.70 m tall, your BMI is 85 ÷ (1.70 × 1.70) = 29.4. If you know your weight in stones and height in feet, our calculator converts everything for you automatically.

In the UK, weight loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide) are licensed for adults with a BMI of 30 or above, or a BMI of 27 to 30 alongside at least one weight-related health condition such as type 2 diabetes, high blood pressure, high cholesterol or sleep apnoea. A prescriber will always assess your full health history, not just your BMI, before deciding whether treatment is appropriate.

BMI is a useful screening tool, but it has limitations. It doesn’t distinguish between muscle and fat, so very muscular people can have a high BMI without excess body fat. It also doesn’t account for age, sex or where fat is stored on your body. That’s why healthcare professionals use BMI alongside other measures, such as waist circumference, blood pressure and blood tests, when assessing your health.

The BMI calculation and categories are the same for men and women. However, women naturally carry more body fat than men at the same BMI, and body composition changes with age, particularly after menopause. This is one reason BMI should be interpreted as part of a broader health assessment rather than a definitive measure on its own.

According to the Health Survey for England, the average adult BMI is around 27.6, which falls within the overweight range. Roughly two thirds of adults in England are living with overweight or obesity, so if your BMI is above the healthy range, you are far from alone — and effective, evidence-based support is available.

The foundations of lowering your BMI are a sustained calorie deficit, regular physical activity (the NHS recommends at least 150 minutes of moderate exercise per week), adequate sleep and managing stress. If lifestyle changes alone haven’t worked and your BMI is 30 or above (or 27 with a weight-related condition), clinically proven weight loss medication prescribed by a UK doctor may help.

Yes. Research shows that people from South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds face higher risks of conditions like type 2 diabetes at lower BMI levels. NICE therefore recommends using a BMI of 23 (rather than 25) as the threshold for increased risk, and 27.5 (rather than 30) for high risk, for people from these backgrounds.

Overweight is defined as a BMI of 25 to 29.9, while obesity is a BMI of 30 or above. Obesity is further divided into class 1 (BMI 30–34.9), class 2 (BMI 35–39.9) and class 3 (BMI 40 or above). Health risks generally increase as BMI rises, but even modest weight loss of 5% of your body weight can meaningfully improve blood pressure, blood sugar and cholesterol.

Possibly. If your BMI is between 27 and 30 and you have at least one weight-related health condition — such as high blood pressure, type 2 diabetes, high cholesterol, sleep apnoea or PCOS — you may still be eligible for weight loss treatment. A BMI below 27 does not qualify for weight loss injections under UK licensing. Complete our free online assessment and a UK-registered prescriber will review whether treatment is right for you.