BMI Calculator
Calculate BMI for adults age 20 and older with metric or US units, then learn what the number can and cannot tell you.
Calculate your estimate
What this tool tells you
Body mass index (BMI) compares weight with height. It is a screening measure used for adults age 20 and older, not a diagnosis or a direct measure of body fat.
How the estimate works
BMI = weight in kilograms ÷ (height in meters × height in meters). Adult categories shown follow the CDC: underweight below 18.5, healthy weight 18.5–24.9, overweight 25–29.9, and obesity range 30 or above.
Important limitations
BMI does not show body composition, where weight is carried, or your overall health. These adult categories are not appropriate for people under age 20, and interpretation may differ during pregnancy or with high muscle mass. Discuss concerns with a clinician.
Frequently asked questions
Is BMI a diagnosis?
No. It is one screening measure. A healthcare professional considers it alongside other information.
Does this calculator work for children or teens?
No. People under age 20 need age- and sex-specific BMI growth charts.
Can I use pounds and inches?
Yes. The calculator converts US units to kilograms and meters before applying the same formula.
Understand your BMI result
These guides explain the adult ranges, what the calculation can tell you, and why it is only one part of a health picture.