How to use the BMI calculator
- Choose metric or imperial units and enter your height and weight.
- Read your BMI, your category and where you sit on the colour scale.
- See the healthy weight range for your height and how far you are from it.
If you have Asian (South, East or Southeast Asian) heritage, switch to the Asian populations cut-offs. Research summarised by the World Health Organization shows that health risks such as type 2 diabetes start at a lower BMI in these populations.
The BMI formula
BMI = 703 × weight (lb) ÷ height (in)²
Example
A person who is 1.70 m tall and weighs 70 kg has a BMI of 70 ÷ (1.70 × 1.70) = 24.2, inside the healthy range. For that height, a BMI of 18.5 to 24.9 corresponds to about 53.5 to 72.3 kg.
BMI categories for adults
| BMI (WHO) | Asian cut-offs | Category |
|---|---|---|
| Below 18.5 | Below 18.5 | Underweight |
| 18.5 – 24.9 | 18.5 – 22.9 | Healthy weight |
| 25 – 29.9 | 23 – 27.4 | Overweight |
| 30 – 34.9 | 27.5 – 32.4 | Obesity class I |
| 35 – 39.9 | 32.5 – 37.4 | Obesity class II |
| 40 and above | 37.5 and above | Obesity class III |
What BMI does not tell you
BMI is a quick screening number, not a diagnosis. It does not separate muscle from fat, so muscular people can show as "overweight". It also does not show where fat is stored, which matters: fat around the waist carries more health risk. For a fuller picture, add your waist-to-height ratio (keep your waist under half your height) or estimate your body fat with our body fat calculator. Read more in our guide what BMI tells you and what it misses.
Who should not use this calculator
- Children and teenagers under 18: use age- and sex-specific growth charts from your doctor or the WHO/CDC.
- Pregnant women: weight gain in pregnancy follows different guidance.
- Very muscular athletes and older adults who have lost muscle: BMI can over- or underestimate risk.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9 (18.5 to 22.9 for people of Asian heritage), according to the World Health Organization.
What is BMI Prime?
Your BMI divided by the upper limit of the healthy range. A value of 1.0 is the top of the healthy range; 1.2 means 20% above it.
Is BMI different for men and women?
The adult formula and categories are the same for men and women, although women usually carry more body fat at the same BMI.
Do you store my height and weight?
No. The calculation runs in your browser; nothing is sent to our servers.
Sources: World Health Organization, "Obesity and overweight" fact sheet; WHO Expert Consultation, "Appropriate body-mass index for Asian populations", The Lancet, 2004; US Centers for Disease Control and Prevention (CDC), "About adult BMI".
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Last reviewed: 2026-11-09. These tools give general information, not medical advice. Talk to a doctor about your health. See our medical disclaimer.