Calculate adult Body Mass Index from height and weight in metric or US units, then view the standard screening categories and limitations.
Your BMI
How Body Mass Index Is Calculated
Body Mass Index (BMI) is weight divided by height squared. In metric units, the calculation is kilograms divided by metres squared. For US customary units, this tool uses the equivalent conversion factor of 703 with weight in pounds and height in inches. The result is compared with the adult screening ranges shown above.
Adult BMI categories
- Underweight: below 18.5
- Normal weight: 18.5 to below 25
- Overweight: 25 to below 30
- Obesity: 30 or higher
Understanding the limits of BMI
BMI is a screening measure, not a diagnosis. It does not directly measure body fat, distinguish muscle from fat, or describe fat distribution. Interpretation can differ for children and adolescents, pregnancy, older adults, athletes, and some medical conditions.
Health note: Do not use one BMI value to diagnose a condition or set a treatment goal. Discuss concerns and individual context with a qualified healthcare professional.
Source and important context
The Centers for Disease Control and Prevention describes adult BMI as a screening measure, not a diagnosis. Its adult categories apply to adults aged 20 and older and should be considered alongside other health information. CDC: Adult BMI Categories. This page provides general educational estimates and is not a diagnosis or a substitute for individualized care. Page information updated: 4 November 2026.
Example and limitations
BMI is a screening measure based on height and weight; it does not directly measure body fat or distinguish muscle from fat. The adult categories are not intended for children or teens.