BMI Calculator

BMI stands for Body Mass Index. It is a screening number calculated from height and weight. For adults, BMI is commonly used to estimate whether a person is underweight, in the normal weight range, overweight, or in the obesity range. It is not a diagnosis and does not directly measure body fat.

In metric units, BMI equals weight in kilograms divided by height in meters squared. In imperial units, BMI equals 703 multiplied by weight in pounds divided by height in inches squared. This calculator shows the formula used after calculation.

For most adults, a BMI from 18.5 to 24.9 is commonly considered the normal or healthy weight range. A BMI below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is in the obesity range. These categories are screening ranges and should be interpreted with health context.

BMI is useful as a quick population-level screening tool, but it is not perfect for every person. It does not distinguish between fat, muscle, bone, or body shape. Athletes, older adults, pregnant people, children, and people with unusual muscle mass may need other measurements and professional guidance.

This calculator uses adult BMI categories. Children and teenagers need BMI-for-age percentiles because healthy ranges change with age and sex during growth. For children, use a pediatric BMI percentile calculator or speak with a healthcare professional.

BMI prime compares your BMI with the upper end of the normal adult BMI range, which is 25. A BMI prime below 1 means BMI is below 25, while a value above 1 means BMI is above 25. It is another way to understand how your BMI compares with the common adult reference range.