HEALTH TOOLS
BMI Calculator UK
Calculate your Body Mass Index using the WHO 2000 classification, the standard used by NHS England. Supports metric and imperial units.
WHO BMI Categories
| BMI Range | Classification | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Nutritional deficiency, immune suppression |
| 18.5 to 24.9 | Healthy Weight | Lowest risk in this range |
| 25.0 to 29.9 | Overweight | Moderately increased risk |
| 30.0 to 34.9 | Obese (Class I) | High risk of type 2 diabetes and cardiovascular disease |
| 35.0 to 39.9 | Obese (Class II) | Very high risk |
| 40.0 and above | Severe Obesity (Class III) | Extremely high risk |
WHO (2000). Obesity: Preventing and Managing the Global Epidemic. Used by NHS England and referenced in NICE clinical guideline CG189.
This calculator is designed for adults aged 18 to 65. It is not suitable for children, pregnant women, or people under 18 (NHS uses age-specific centile charts for children). South Asian, Chinese, and Black African populations may have lower BMI thresholds for health risk. If your BMI is below 16 or above 40, speak to your GP or contact NHS 111.
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