BMI Calculator
Calculate body mass index from height and weight using metric or US customary units. The result provides an adult BMI category and an estimated healthy-weight range for the entered height.
BMI formulas
- Metric:
BMI = weight in kilograms / height in metres squared. - US customary:
BMI = 703 x weight in pounds / height in inches squared.
For example, an adult who weighs 70 kg and is 1.75 m tall has a BMI of about 70 / 1.75^2 = 22.9.
Adult BMI categories
For adults aged 20 and older, the US Centers for Disease Control and Prevention lists these screening categories:
- below 18.5: underweight;
- 18.5 to 24.9: healthy weight;
- 25.0 to 29.9: overweight; and
- 30.0 or higher: obesity.
The CDC further separates obesity into classes. See the CDC adult BMI calculator and category guidance for the complete ranges.
How to interpret your result
BMI is a screening measure, not a diagnosis. It does not directly measure body fat and may not reflect individual differences in muscle mass, body composition, pregnancy, age-related changes, or health history. Children and teenagers require age- and sex-specific BMI percentiles rather than the adult categories used here.
Use the result as one piece of information and discuss health concerns with a qualified healthcare professional. This calculator does not replace medical evaluation or advice.
Measurement tips
- Measure height without shoes and weight in light clothing when possible.
- Use the same unit system for every measurement.
- Recheck unusually high or low results for an input or unit mistake.
- Focus on trends and overall health context rather than a single isolated number.
Related calculators
The body fat calculator, ideal weight calculator, and BMR calculator provide different estimates. None of them should be treated as a medical diagnosis.