Percentile guide
Your child's growth chart, made easier to read
Wondering where a recent measurement sits on the growth chart? Choose Baby, Boy, or Girl, add the age and measurement, and we'll place it on the matching WHO or CDC curve with its percentile and z-score.
Percentiles show where a measurement lies among children of the same age and sex in the selected reference. The same height can have a different meaning at age 5, 8, or 12, so age, sex, indicator, and reference all matter.
Use Baby from birth to 24 months, when recumbent length is normally measured. WHO Child Growth Standards cover infant indicators, WHO Growth Reference 2007 covers school-age children, and CDC 2000 covers U.S. children where supported.
01
Choose the child
Start with Baby, Boy, or Girl so the sex- and age-specific reference is correct.
02
Enter the measurement
Add age and the required length, height, weight, or head circumference.
03
Read the band
Compare the plotted point with P3, P15, P50, P85, and P97.
Choose the right growth chart
Choose Baby for birth to 24 months, or Boy or Girl for an older child or teenager. Then select length-for-age, height-for-age, weight-for-age, weight-for-length, or head circumference-for-age when the reference supports it.
Early growth changes quickly, so infant age is entered in months and length is measured lying down. For older children, enter both years and months to position the point more accurately.
Boys and girls use separate medians and percentile curves. Always select the correct curve sex before entering the measurement.
Keep the reference label with any saved result because WHO and CDC can produce different percentiles for the same measurement.
WHO, CDC, and age ranges
WHO Child Growth Standards are used for infant length-for-age, weight-for-age, weight-for-length, and head circumference-for-age. WHO Growth Reference 2007 covers height-for-age from 5 to 19 years and weight-for-age from 5 to 10 years. CDC 2000 covers supported indicators from 2 to 20 years.
WHO and CDC are separate references. Compare their results only when you intentionally want to examine how the systems differ, and always keep the source and age range visible.
How to read a percentile and z-score
P50 is the median: half of the reference population is above it and half is below it. A z-score expresses the same position in standard-deviation units. Neither value is a diagnosis on its own.
One point is a snapshot. A consistent pattern over time is usually more informative than an isolated result. If a measurement moves sharply across bands, save the age, value, percentile, z-score, and source for discussion with a qualified clinician.
This calculator is for child growth percentiles. Use separate tools for adult height prediction, BMI, or visual height comparison.
What to save with a result
Save the child's age, curve sex, measurement, unit, indicator, reference source, and date. A percentile alone is easy to misread once its age and reference are lost.
Keep measurement technique consistent. Shoes, posture, time of day, scale calibration, and recumbent length versus standing height can all shift the plotted point.
For clinical discussion, bring earlier measurements too. A pattern across visits is more useful than a single dot.
Check the source before using the result
Verify the indicator, age range, and reference. Length-for-age, height-for-age, weight-for-age, weight-for-length, BMI-for-age, and head circumference-for-age are different measurements and must not be interchanged.
WHO standards and references describe international populations; CDC tables describe U.S. pediatric references. Read every result with its own labels, units, and age limits.
The source tables below the visualization make it easier to confirm the selected chart before relying on a percentile.
Common reading mistakes
Do not treat one point as the whole story. A child can be above or below the median and still follow a stable personal pattern.
Do not mix standing height with recumbent length. Babies are normally measured lying down, while older children are normally measured standing.
Do not compare boys and girls on the same curve. The medians and percentile curves are sex-specific.
What this page is best for
Use this page for quick reference checks: estimate a percentile and z-score, confirm the active WHO or CDC reference, and see how a measurement sits among nearby bands.
It does not replace medical judgment. Measurement technique, illness, growth history, family background, nutrition, and clinical context all matter. Ask a qualified clinician about an unexpected, rapidly changing, or concerning pattern.