BMI calculator
Your body mass index and healthy weight range, in metric or imperial units.
- Your BMI
- 22.9
- Category
- Healthy weight
- BMI 18.5–24.9
- Healthy weight for your height
- 56.7–76.3 kg
For information only, not medical advice. BMI is a rough screening measure. Talk to a doctor or other health professional about your own health.
How it works
What BMI tells you, and what it doesn't
Body mass index compares your weight with your height:
BMI = weight (kg) ÷ height (m)²
| BMI | Category (WHO, adults) |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30 or more | Obesity |
BMI is popular because it is quick and needs no equipment, and across large groups of people it tracks health risks reasonably well. For individuals it is a starting point. It can't see the difference between muscle and fat, it doesn't account for age, sex or ethnicity, and it says nothing about fitness, diet or where fat is stored.
If your BMI is outside the healthy range, or you're worried about your weight, a doctor can look at the full picture, including waist measurement, blood pressure and blood tests.
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Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in meters squared. For 70 kg and 1.75 m: 70 ÷ (1.75 × 1.75) = 22.9. In pounds and inches, multiply weight ÷ height² by 703.
What is a healthy BMI?
For most adults the World Health Organization classifies 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight and 30 or more as obesity. Some health services use lower thresholds for people of South Asian, Chinese, Middle Eastern, Black African or African-Caribbean background.
Is BMI accurate?
It is a quick screening measure, not a diagnosis. BMI doesn't tell fat from muscle, so very muscular people can score as overweight, and it says nothing about where fat sits on the body. Waist size and other checks give a fuller picture.
Can children use this calculator?
No. For children and teenagers, BMI is compared with growth charts for their age and sex, and the adult categories don't apply. Ask a doctor, nurse or school health service.
Is my data stored?
No. The calculation happens in your browser and your height and weight are never sent anywhere.