BMI Percentile Calculator for Kids (CDC, 2-20y)
Enter your child's sex, age, height, and weight. BMI-for-age applies from 2 to 20 years and uses the CDC's own category cutoffs -- shown as CDC's categories, not this site's.
BMI
16.0
CDC category
Healthy weight
BMI-for-age percentile
55th percentile
z-score +0.13
| Age | P3 | P10 | P25 | P50 | P75 | P90 | P97 |
|---|---|---|---|---|---|---|---|
| 8y 0m | 13.6 | 14.1 | 14.8 | 15.8 | 17.0 | 18.7 | 21.2 |
Worked example
An 8-year-old boy, 130cm and 27kg: BMI = 27 / 1.30² = 16.0. At 96 months the CDC table gives L=-3.191, M=15.77, S=0.1017, so z = 0.13, the 55th percentile -- inside the CDC's healthy-weight range (5th to below the 85th).
CDC category cutoffs
| BMI-for-age percentile | CDC category |
|---|---|
| Below 5th | Underweight |
| 5th to below 85th | Healthy weight |
| 85th to below 95th | Overweight |
| 95th and above | Obesity |
For an adult's own body composition, not a child's, see Macrograms' body-fat calculator.
Frequently Asked Questions
Why does BMI work differently for kids than adults?
An adult's BMI is compared to fixed cutoffs (18.5, 25, 30) because adult body composition is roughly stable. A child's BMI changes a lot just from normal growth -- it typically rises in infancy, falls through the preschool years, then rises again. So the CDC compares a child's BMI to other children the same age and sex, as a percentile, rather than to a fixed number.
What are the CDC's category cutoffs?
These are the CDC's own published categories, not a scale this site invented: below the 5th percentile is underweight, 5th to below the 85th is healthy weight, 85th to below the 95th is overweight, and 95th and above is obesity.
Is BMI-for-age the whole picture?
No -- it's a screening tool, not a diagnosis. Muscular kids can read high on BMI without a body-composition problem, and BMI doesn't distinguish fat from muscle. Pediatricians use it alongside growth history, family patterns, and a physical exam, not on its own.
What about adult BMI, for a parent?
Adult BMI uses the fixed cutoffs above rather than an age comparison. Macrograms' body-fat calculator covers an adult's own body composition in more detail than a single BMI number.
These calculators estimate from published population reference data (the CDC and WHO growth charts) and published rules of thumb -- not a diagnosis, and not a substitute for your pediatrician, who tracks your child's own growth curve over time and knows their history.