How to use this tool
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI, which category it falls in and the weight range considered healthy for your height.
How BMI is calculated
BMI is your weight in kilograms divided by your height in metres squared. A person who is 1.72 m tall and weighs 70 kg has a BMI of 70 ÷ (1.72 × 1.72) = 23.7. In imperial units the formula is weight in pounds × 703 ÷ height in inches squared.
BMI categories
| Category | WHO (general) | Asian populations |
|---|---|---|
| Underweight | below 18.5 | below 18.5 |
| Healthy | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 27.4 |
| Obese | 30 and above | 27.5 and above |
People of South Asian, Chinese and other Asian backgrounds tend to have higher health risks at a lower BMI, which is why the WHO and bodies such as NICE in the UK suggest lower cut-offs for these groups.
Limits of BMI
BMI can't tell muscle from fat, so athletes may score as overweight while being lean. It also doesn't account for where fat is stored. Waist size is a useful second check. BMI charts for children and teenagers use age and sex percentiles instead, so this calculator is for adults only.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9. For people of Asian background, many guidelines use 18.5 to 22.9.
How do I calculate BMI in pounds?
Multiply your weight in pounds by 703, then divide by your height in inches squared.
Is BMI accurate for muscular people?
Not always. Muscle weighs more than fat, so very muscular people can have a high BMI without excess fat.
Can children use this BMI calculator?
No. Children need BMI-for-age charts, which compare them with others of the same age and sex.
Sources and references
- World Health Organization: Obesity and overweight
- NICE guideline NG246: Overweight and obesity management
- CDC: About adult BMI