What BMI measures
Body mass index (BMI) relates weight to height. It is widely used as a simple screening measure because the calculation is quick and consistent. It does not directly measure body fat, fitness, nutrition or health.
Reading the number
Adult BMI results are often grouped into broad ranges. These ranges can help identify population-level patterns, but the same number can mean different things for different people. Age, muscle mass, pregnancy, body composition, ethnicity and medical history may affect interpretation. Children and teenagers require age- and sex-specific growth references rather than adult cut-offs.
Use BMI as a starting point
A useful follow-up is to consider other information such as waist measurement, blood pressure, activity level, sleep, laboratory results and changes over time. One isolated number should not become a diagnosis or a target by itself.
Check your inputs
- Measure height without shoes.
- Use a reliable scale on a level surface.
- Select the correct metric or imperial units.
- Recheck an unexpected result before acting on it.
When to get professional guidance
Speak with a qualified healthcare professional if the result concerns you, if weight is changing unexpectedly, or if you need advice for a child, pregnancy, an eating disorder, medication or an existing health condition.
The BMI calculator is an informational screening tool. It cannot assess an individual's health or replace a clinical evaluation.