Free BMI Calculator for Adults in United Kingdom
Enter your weight in kilograms and height in centimetres or feet/inches to calculate Body Mass Index (BMI), see the standard adult category, and view a height-based healthy-weight reference range.
Enter your measurements to see your BMI, category and healthy-weight reference range.
How BMI Is Calculated
BMI compares body weight with height using a simple formula: BMI = weight in kilograms ÷ height in metres². For example, a person who weighs 70 kg and is 1.73 m tall has a BMI of about 23.4.
For adults, the commonly used international categories are: underweight below 18.5, healthy range 18.5 to 24.9, overweight 25 to 29.9, and obesity from 30 upward. BMI is a screening measure rather than a diagnosis.
United Kingdom and South Asian context
South Asian populations can develop diabetes and cardiovascular risk at lower BMI values than some other populations. That does not mean a BMI number alone diagnoses risk. It means people in United Kingdom may benefit from interpreting BMI together with waist size, blood pressure, blood glucose, family history, activity and professional medical advice.
What your healthy-weight range means
The calculator converts the standard BMI range of 18.5 to 24.9 into a weight range for your height. It is a broad reference, not a single “perfect” target. Muscle mass, body frame, age and individual health can make a meaningful difference.
BMI Calculator United Kingdom: Common Questions
Is BMI different for men and women?
The adult BMI formula itself is the same for men and women. Body composition can differ, so BMI should be interpreted alongside other health information rather than used as a complete assessment.
Can I calculate BMI using feet and kilograms?
Yes. This calculator lets you enter height in feet and inches while keeping weight in kilograms, which is a common combination in United Kingdom. The tool converts your height to metres automatically before applying the BMI formula.
Is BMI accurate for muscular people?
BMI cannot distinguish fat mass from muscle mass. A muscular person may have a high BMI without the same body-fat profile as someone with less muscle. Waist measurements or a body-composition assessment can add useful context.
Should I use BMI for weight-loss planning?
BMI can provide a starting reference, but daily calorie needs depend on age, body size and activity. For energy planning, use the Calorie Calculator United Kingdom or calculate your TDEE.