Works out your body mass index from height and weight, with the World Health Organization categories for adults.
Enter height in cm or in feet + inches — whichever you prefer.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5–24.9 |
| Overweight | 25–29.9 |
| Obesity | 30 or above |
For adults. BMI is a screening measure, not a diagnosis: it does not distinguish muscle from fat and is interpreted differently in athletes, older adults, pregnancy and children.
What is BMI?
Body mass index relates weight to height (kg/m²) and is the standard first-pass screen for underweight, healthy weight, overweight and obesity in adults. It is quick and useful across populations, even though it does not measure body fat directly.
When can BMI be misleading?
BMI can overestimate body fat in muscular athletes and underestimate it in older adults who have lost muscle. It is also not used the same way in pregnancy, and children are assessed with age- and sex-specific percentile charts instead.
What should I do with my result?
Treat BMI as a starting point for a conversation, not a diagnosis. Waist circumference, blood pressure, blood sugar and cholesterol all add important context that a clinician can assess.