Body Mass Index (BMI) is a tool for indicating weight status in adults and for assessing underweight, overweight, and risk for overweight in children and teens.

For adults over 20 years old, BMI is a measure of body weight adjusted for height.

BMI for children and teens (2 to 20 years old) is calculated differently than adult BMI. Also called "BMI-for-age," measurements are gender and age specific, due to a child's rate of growth and development.

BMI calculators

From The Pennsylvania Medical Society

• BMI Calculator
  The BMI is a widely respected standard to tell if you are overweight.
• BMI Wheel
  One side of this double-sided wheel calculates BMI for children—20 to 80 pounds—while the other side calculates BMI for adolescents and adults, 80 to 350 pounds. The CD-sized BMI Wheels are constructed of a durable plastic material and are available for $5.50 at www.pamedsoc.org/store.

From The Children's Nutrition Research Center (CNRC)

• Children's BMI-percentile-for-age calculator
  The BMI-percentile-for-age calculator automatically adjusts for differences in height, age, and gender, making it a good tool for evaluating a growing child's weight.

• Adult BMI Calculator
• Child and Teen BMI Calculator
• Tools for Calculating BMI