BMI Calculator
Free BMI calculator with metric and imperial units. Enter height and weight to get your body mass index, WHO category and healthy weight range instantly.
About the BMI Calculator
Body Mass Index (BMI) is a quick screening measure that compares your weight to your height. It is widely used by the WHO, doctors and insurers to flag whether a person is in a healthy weight range for their height. This calculator supports both metric and imperial units, shows your WHO category and — often more useful — the healthy weight range for your height, not just a single number.
The BMI formula
BMI = weight (kg) ÷ height² (m²)
The standard adult categories are: under 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 or above is obesity.
Limitations worth knowing: BMI does not distinguish muscle from fat, so very muscular athletes often read "overweight" despite low body fat. It also does not account for age, sex or fat distribution. Treat BMI as one data point, not a diagnosis — for a full picture, combine it with waist measurement and a professional check-up.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ falls in the obesity range. Individual context matters, so use the number as a screening signal rather than a verdict.
How is BMI calculated for children and teens?
For ages 2–19, BMI is compared against growth charts by age and sex (BMI-for-age percentile) instead of fixed adult categories. This calculator is intended for adults 20 and over.
Is BMI accurate for muscular people?
Not entirely. Muscle is denser than fat, so athletes and bodybuilders frequently score in the "overweight" range with normal body fat. Waist-to-height ratio and body composition tests fill that gap.
Is my health data private here?
Yes. Height and weight are processed only on your device. The page contains no trackers and sends nothing to a server.