BMI Calculator UK
Our free UK BMI calculator instantly checks whether your weight falls within a healthy range based on NHS guidelines. Enter your height and weight to receive your BMI score and weight category — Underweight, Healthy, Overweight, or Obese — in seconds with no account needed.
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How to Calculate Your BMI Using NHS Guidelines
This calculator uses the international standard BMI formula: BMI = weight (kg) ÷ height (m)². Enter your height in centimetres and your weight in kilograms to receive your BMI score. The result is benchmarked against the four NHS weight categories: Underweight (under 18.5), Healthy Weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). The calculator supports both metric (kg/cm) and imperial (lbs/inches) inputs.
Frequently Asked Questions
What is a healthy BMI range for adults in the UK?
According to NHS guidelines, a healthy BMI for adults is between 18.5 and 24.9. Below 18.5 is classified as underweight, 25 to 29.9 is overweight, and a BMI of 30 or above is classified as obese.
Is BMI an accurate measure of health for UK adults?
BMI is a useful screening tool but does not directly measure body fat, muscle mass, or distribution of fat. Athletes often have a high BMI due to muscle rather than fat. The NHS recommends using BMI alongside waist circumference and other health metrics.
How do I manually calculate my BMI in the UK?
To calculate BMI manually, divide your weight in kilograms by your height in metres squared. For example, if you weigh 75 kg and are 1.75 m tall: 75 ÷ (1.75 × 1.75) = BMI of 24.5, which falls in the healthy range.
Does BMI use different thresholds for men and women in the UK?
The standard BMI formula and NHS thresholds are the same for men and women. However, women naturally carry slightly more body fat than men at the same BMI. Some clinicians also assess waist-to-hip ratio alongside BMI for a fuller health picture.
What BMI is classified as obese in the UK?
The NHS classifies a BMI of 30 or above as obese. A BMI of 40 or above is classified as severely (morbidly) obese. If your BMI falls in these ranges, your GP can discuss healthy weight management options including dietary support and physical activity programmes.