What Is the Equation for BMI?

Use height and weight to calculate your BMI.

BMI stands for Body Mass Index. This is a simple ratio calculated from your height and weight. It is used, with other indicators, as a guide to a healthy weight and body size.

Metric Conversion

The BMI formula uses your weight in kilograms and your height in meters. You may need to convert from Imperial measurements. 1 kilo is 2.2 lbs and one meter is 3.28 feet. Many online conversion sites will work this out for you, or you can divide your weight in lbs. by 2.2 (to determine your weight in kilograms) and divide your height in feet by 3.28 (to determine your height in meters).

Calculating BMI

Calculate weight divided by height squared.

To find your BMI, first square your height in meters; that is, multiply it by itself. Then divide your weight in kilograms by this number. A normal BMI for adults ranges from 18.5 to 25, although other factors such as a person's state of health and culture are often taken into account when assessing normality.

BMI in Children and Teens

Children and teens have bodies, and BMIs, that change with growth. There is no set normal range. To determine normal BMI for children, a doctor or nutritionist would refer to a range of charts showing normal ranges for different age groups.

References

• World Health Organisation: BMI classification
• Centers for Disease Control and Prevention: Assessing Your Weight

Resources

• Mayo Clinic: BMI calculator