BMI Calculator for Kids

How BMI for Children Works

For adults, BMI is interpreted with fixed categories. For children and teens (ages 2–19), BMI must be compared to age- and sex-specific percentiles.

The BMI formula

BMI = (Weight in lbs ÷ Height in inches²) × 703

Step-by-step

1. Enter the child's weight in pounds.
2. Enter the child's height in inches.
3. Enter the child's age in years.
4. The calculator computes the raw BMI value.

Worked example

80 lbs, 55 inches tall, age 10. BMI = (80 ÷ 3025) × 703 ≈ 18.6.

Interpreting children's BMI

For children, a BMI of 18.6 might be in a different percentile depending on age and sex. Use the CDC BMI-for-age growth charts to find the exact percentile:

• Below 5th percentile: underweight
• 5th to 85th percentile: healthy weight
• 85th to 95th percentile: overweight
• Above 95th percentile: obese

Consult a pediatrician for proper assessment — this calculator provides the raw BMI only.