BMI Calculator for Adults
Enter your height and weight in metric or imperial units to get your Body Mass Index, its WHO adult category and the weight range that corresponds to a BMI of 18.5–24.9 at your height.
How to calculate BMI
- Choose metric (cm, kg) or imperial (feet, inches, pounds) units.
- Enter your height and weight.
- Read your BMI and its category. Your row is highlighted in the WHO table.
- Check the healthy weight range for your height and the worked formula below it.
Benefits
- Imperial inputs are converted with the exact international inch and pound definitions before the calculation.
- Shows the full WHO adult classification, including the three underweight and three obesity grades.
- Explains the calculation step by step, so you can check it.
Limitations
- BMI is a screening measure only. It doesn't measure body fat and is not suitable for children, teenagers, pregnant people or very muscular athletes.
- Uses WHO's international cut-offs. Some health services use lower thresholds for certain populations.
Privacy and security
Height and weight are used only in this browser tab to work out the result. They are not stored, not sent anywhere and not included in analytics.
Read our privacy policy for details about the site as a whole.
Frequently asked questions
What is the BMI formula?
BMI is weight in kilograms divided by height in metres squared. For 70 kg and 1.75 m that is 70 ÷ 1.75² ≈ 22.9. Imperial values are converted to kilograms and metres first.
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so muscular people can have a high BMI with little body fat. Waist measurements or body-composition tests give more useful information for them.
Can I use this for a child?
No. Children and teenagers are assessed with BMI-for-age percentiles that depend on age and sex, not with the adult categories shown here.