Calculator
Baby and child growth percentile calculator
Enter your child’s age, sex, weight and length or height to see where they fall on the growth charts pediatricians use: the WHO standards from birth to 2 years and the CDC charts from 2 to 20 years, as the CDC recommends. A percentile compares your child with others of the same age and sex; the trend over time matters more than any single reading.
Source: Centers for Disease Control and Prevention · World Health Organization
Calculate percentiles
How the percentile is calculated
Both chart sets publish three numbers for each age and sex, called L, M and S. The calculator turns your child’s measurement into a z-score with z = ((X ÷ M)^L − 1) ÷ (L × S), then converts the z-score to a percentile. Values between listed ages are interpolated.
Why WHO under 2 and CDC after
The CDC recommends the WHO standards for children under 2 because they describe how healthy breastfed infants grow in optimal conditions. From 2 years, US clinicians switch to the CDC charts. You may see a small jump in percentile at the switch; that comes from switching charts, and your child hasn’t changed.
Common questions
What does the 50th percentile mean?
Half of children the same age and sex weigh (or measure) less, and half more. The 90th percentile means 90% are smaller. A percentile describes size, not health.
Which growth charts does this use?
The WHO Growth Standards for birth to 24 months and the CDC growth charts from 2 to 20 years, the combination the CDC recommends for use in the US.
Is a low or high percentile a problem?
Not by itself. Doctors look at the trend over several visits: a child who stays on their own curve is usually growing well. Crossing several percentile lines, up or down, is worth discussing at a checkup.
Sources
- WHO Growth Standards are recommended for use in the U.S. for infants and children 0 to 2 years of age. Centers for Disease Control and Prevention. Checked 2026-09-25.
- WHO Child Growth Standards: weight-for-age percentiles, 0-24 months. World Health Organization, data files hosted by CDC/NCHS. Checked 2026-09-18.
- CDC growth chart data files (LMS parameters), ages 2-20 years. Centers for Disease Control and Prevention, NCHS. Checked 2026-09-25.