Height & weight
Adult screening only — not medical advice, and not for children or pregnancy.
BMI
About this BMI calculator
Body mass index (BMI) is weight divided by height squared. It is a quick adult screening tool used by the WHO, not a measure of body fat and not a diagnosis. Athletes can land in “overweight” with little fat; older adults can have a “healthy” BMI with low muscle.
This page uses the adult WHO bands and also shows a weight range that would put BMI between 18.5 and 24.9 at your height. It is not for children, teens or pregnancy — those use different charts. Nothing is sent to a server.
The BMI formula
Metric: divide kilograms by height in metres squared. A person 170 cm and 70 kg has BMI = 70 ÷ 1.70² ≈ 24.2.
Imperial: multiply pounds by 703, then divide by height in inches squared. Same person at 5 ft 7 in and 154 lb: 703 × 154 ÷ 67² ≈ 24.1.
BMI = 703 × lb / in²
WHO adult BMI categories
| BMI | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| ≥ 40 | Obesity class III |
How to calculate BMI
- Choose units: Metric (cm, kg) or imperial (ft, in, lb). English defaults to imperial; other languages default to metric.
- Enter height and weight: Use current measurements, without shoes. For imperial, feet and leftover inches.
- Read BMI and category: The number, WHO band and a healthy weight range update as you type.
Frequently asked questions
What is BMI?
BMI is body mass index: weight (kg) divided by height (m) squared. It estimates whether weight is low, healthy, high or very high for height in adults.
Is BMI accurate for athletes?
Not always. BMI cannot tell fat from muscle. A muscular person may be classed overweight. Waist size and a clinician’s assessment add context.
Why metric and imperial?
The formula is the same. Imperial uses the 703 constant so pounds and inches give the same BMI as kilograms and metres.
Is this medical advice?
No. BMI is a screening number. It is not for children, and it does not replace a doctor. If you are worried about weight or health, speak to a professional.