BMI Calculator for Kids
Find a child's BMI and see where it sits on the CDC growth charts. Enter your child's sex, age, weight, and height, and this calculator returns their BMI plus the underweight, healthy, overweight, and obese ranges for their age and sex.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Percentile cutoffs are approximate values based on CDC 2000 growth charts.
- Valid for ages 2–19 only. Use the adult BMI calculator for those 20 and older.
- Not a substitute for medical evaluation by a qualified healthcare provider.
Formula
BMI = weight (kg) / height (m)²
Category determined by CDC age- and sex-specific BMI percentile tables
- A child's BMI uses the same weight ÷ height² formula as adults, but the result is interpreted differently.
- For children and teens, BMI is compared to CDC growth charts for the same age and sex rather than fixed adult cut-offs.
- Below the 5th percentile is underweight, 5th–85th is healthy, 85th–95th is overweight, and at or above the 95th is obese.
- This is why a healthy BMI for a 6-year-old is much lower than for a 16-year-old.
- It is a screening tool only — a paediatrician should interpret a child's growth in context.
10-year-old boy, 32 kg, 138 cm
Inputs
- Sex: male
- Age: 10 years
- Weight: 32 kg
- Height: 138 cm
BMI = 32 ÷ 1.38² ≈ 16.8, which falls in the healthy range for a 10-year-old boy (about 14.0–19.4).
Frequently asked questions
How is a child's BMI different from an adult's?
The formula is the same, but a child's BMI is read against age- and sex-specific percentile charts instead of the fixed adult categories.
What is a healthy BMI percentile for kids?
The 5th to 85th percentile for the child's age and sex is considered a healthy weight under CDC guidelines.
Why does age matter so much?
Children's body composition changes rapidly as they grow, so a healthy BMI number rises steadily from toddlerhood through the teen years.
My child is above the 85th percentile — what should I do?
Talk to your paediatrician. They can confirm the reading, look at growth trends, and advise on diet and activity if needed.
What ages does this cover?
It is designed for ages 2 to 19. For adults 20 and older, use the standard adult BMI calculator.
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