Weight tool
BMI Calculator
Body mass index is a quick screening number, not a verdict on your health. Enter your height and weight to see your BMI and the weight range the World Health Organization calls healthy for your height. Add your waist for a second, often more telling, measure.
How this works
What BMI means
BMI is your weight in kilograms divided by your height in metres, squared. For adults, the WHO bands are under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight and 30 or more obesity. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, the NHS uses lower thresholds of 23 and 27.5.
BMI = kg / m²
Where BMI falls short
BMI cannot tell muscle from fat, so it overstates risk for muscular people and can understate it for older adults who have lost muscle. It is not meant for children, during pregnancy, or for some health conditions. Use it as one clue among several.
Why your waist matters
Fat stored around the middle is more closely linked to heart disease and type 2 diabetes than weight alone. NICE and the NHS suggest keeping your waist to less than half your height. Measure halfway between your lowest rib and the top of your hips, after breathing out normally.
References
- World Health Organization. Obesity and overweight. Fact sheet. Read the fact sheet
- National Institute for Health and Care Excellence (2022 update). Obesity: identification, assessment and management. Clinical guideline CG189. Read the guideline
For healthy adults. This is general information, not medical advice.