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BMI calculator
Free · runs in your browser · updated 2026-07-05
How to use the bmi calculator
- Choose unitsMetric (cm and kg) or imperial (feet/inches and stones/pounds).
- Enter height and weightMeasured without shoes is most accurate.
- Check your categoryYour BMI is shown against NHS adult ranges.
Frequently asked questions
What is a healthy BMI in the UK?
For most adults, the NHS defines 18.5 to 24.9 as the healthy range. Below 18.5 is underweight, 25 to 29.9 overweight, and 30 or above obese.
Is BMI accurate for everyone?
No — it doesn't distinguish muscle from fat, so muscular people can score 'overweight' while healthy. Thresholds are also lower for some ethnic groups (23+ counts as increased risk for people of South Asian, Chinese, Black African and African-Caribbean backgrounds, per NICE guidance).
How do I lower my BMI safely?
The NHS recommends a modest calorie deficit, more physical activity and gradual loss of around 0.5–1 kg a week. Speak to your GP before major changes, especially with health conditions.
Does BMI apply to children?
Not with adult thresholds — children's BMI is assessed against age- and sex-specific centile charts. Use the NHS child BMI checker instead.
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