This BMI calculator computes body mass index from metric height and weight and shows the standard adult category. It offers a quick screening number, not a diagnosis or a complete assessment of body composition or health.
How to use this calculator
Enter weight in kilograms, height in centimeters, and age. The adult category is shown only for ages 20 and older. For children and teenagers, BMI requires age- and sex-specific percentiles that this simple calculator does not provide.
Formula & calculation method
BMI = weight in kilograms / (height in meters)²Height is converted from centimeters to meters before squaring. Adult results are grouped as underweight below 18.5, healthy range from 18.5 to below 25, overweight from 25 to below 30, and obesity at 30 or above.
Worked example
A weight of 70 kg and height of 170 cm gives a BMI of about 24.2, which lies in the standard adult healthy range. The category describes the index only and does not measure fat distribution or fitness.
Why this is useful
The tool provides a consistent calculation and immediate context for the numeric result. Clear category boundaries make it easier to track a screening measure over time when measurements are taken consistently.
Limitations to keep in mind
BMI does not distinguish muscle from fat or account for fat distribution. It may be less informative during pregnancy, for athletes with high muscle mass, and for some ages or body types. Discuss health concerns with a qualified professional.
Frequently asked questions
Is BMI a body-fat percentage?
No. BMI is a weight-to-height ratio. It does not directly measure body fat, muscle mass, or fat distribution.
Can children use this calculator?
The numeric formula can be calculated, but adult categories do not apply to people under 20. Pediatric interpretation needs age- and sex-specific growth references.
What units does the calculator use?
It uses kilograms and centimeters. Convert your measurements first if they are recorded in pounds and inches.