In short: Body mass index (BMI) is weight in kilograms divided by height in meters squared; for adults, 18.5–24.9 is the WHO “healthy weight” range.
About BMI Calculator
Body Mass Index is weight in kilograms divided by height in meters squared. It is the most widely used quick screen for whether an adult’s weight is in a range associated with lower health risk, and it is what doctors, insurers and public-health statistics usually mean by “healthy weight”.
This calculator works in metric or imperial units, places your result on the World Health Organization adult scale (underweight below 18.5, healthy 18.5–24.9, overweight 25–29.9, obesity 30 and above), and shows the weight range that corresponds to a BMI of 18.5–24.9 at your height. Because BMI cannot distinguish muscle from fat, treat it as a starting point for a conversation with a professional rather than a verdict.
How to use BMI Calculator
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI, its WHO category and the marker on the scale.
- Check the healthy weight range for your height shown below the result.
Examples
175 cm and 70 kg: 70 ÷ 1.75² = 22.9, in the healthy range.
5 ft 9 in and 154 lb gives a BMI of about 22.7. The imperial formula is 703 × lb ÷ in².
Frequently asked questions
Is BMI accurate for athletes?
Often not. Muscular people can have a high BMI with low body fat. Waist circumference or body-composition measurements give extra context.
Can I use this for children?
No. Children and teens are assessed with age- and sex-specific BMI percentiles, not the adult categories shown here. Ask a pediatrician.
Do the categories differ for Asian populations?
Some health bodies use lower cut-offs for people of Asian descent (for example 23 for overweight) because health risks rise at lower BMIs. Your doctor can advise which applies to you.
Is my data stored?
No. The calculation runs in your browser and nothing is saved or sent.
Updated November 2026 · Free, no signup · How we build and test tools