Height Percentile Calculator

Enter your child's sex, age, and height to estimate their height-for-age percentile using CDC growth-chart reference data (ages 2-20), plus how their height compares to the reference median. This is an educational estimate, not a substitute for a pediatrician's growth assessment.

Quick Facts

Percentile method
Z = (height − reference median) ÷ reference SD
The z-score is converted to a percentile with the standard normal distribution.
Typical range
5th–95th percentile
About 90% of children of the same age and sex fall in this band — it is not a pass/fail cutoff.
Age coverage
2–20 years (CDC charts)
Infants and toddlers under 2 are tracked on separate WHO length-for-age standards, not this tool.

Your Results

Calculated
Height Percentile
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Compared to children of the same age and sex
Height-for-Age Z-score
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Standard deviations from the reference median
Reference Median Height
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Expected 50th-percentile height at this age/sex
Difference from Median
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How far above or below the median

Ready

Enter your child's sex, age, and height, then press Calculate.

How the Child Height Percentile Calculator Works

Pediatric growth charts compare a child's height to a reference population of children of the same age and sex, because "normal" height changes constantly through childhood and differs between boys and girls. This calculator estimates that comparison with a standard height-for-age z-score method built on CDC growth-chart reference data for ages 2 through 20 — the same age range covered by the CDC's stature-for-age charts used in U.S. pediatric practice.

The z-score and percentile method

For the child's exact age (in years and months) and sex, the calculator looks up the reference median height and standard deviation (SD) from CDC growth-chart data, interpolating between the nearest reference ages. It then computes a z-score: z = (child's height − reference median height) ÷ reference SD. The z-score is converted into a percentile using the cumulative standard normal distribution — a z-score of 0 is the 50th percentile, +1 is roughly the 84th percentile, and −1 is roughly the 16th percentile. This mirrors how official CDC/WHO growth charts translate a measurement into a percentile line, though the official charts use a slightly more precise curve-fitting method (LMS) for each single month of age.

Reading and using the percentile

A percentile describes rank, not health. A child at the 25th percentile for height is shorter than about 75% of same-age, same-sex peers — that alone does not mean anything is wrong, especially if both parents are shorter than average. What pediatricians watch most closely is the trend across multiple visits: a child who consistently tracks near the same percentile line is usually growing normally, while a child who drops or rises across two or more major percentile bands between checkups is more likely to warrant further evaluation.

Limitations of this estimate

This calculator is an educational approximation, not a diagnostic tool. It does not apply below age 2 (infants and toddlers are tracked on separate WHO length-for-age standards), it uses reference values interpolated at yearly intervals rather than the CDC's full monthly LMS tables, and it cannot account for family height patterns, ethnicity, prematurity, or underlying medical conditions. For an official percentile and growth trajectory, ask your pediatrician to plot the measurement on the standard CDC or WHO growth chart used at well-child visits.

Frequently Asked Questions

What does a child's height percentile mean?
A height percentile compares a child's height to other children of the same age and sex in a reference population. A child at the 60th percentile is taller than about 60% of same-age, same-sex peers and shorter than about 40% of them. It describes relative size, not health status by itself.
What formula does this calculator use?
It calculates a height-for-age z-score, z = (height − reference median height) ÷ reference standard deviation, using CDC growth-chart reference values interpolated for the child's exact age and sex, then converts that z-score to a percentile with the standard normal distribution.
Is a low or high percentile a problem?
Not necessarily. Percentiles below the 5th or above the 95th are simply less common and are usually a reason to mention it at a checkup, but a child's own growth trend over time — staying near a consistent percentile curve — matters more than any single measurement. Sudden crossing of two or more percentile lines is what most often prompts further evaluation.
Does this work for children under 2 years old?
No. Infants and toddlers under 24 months are tracked on separate WHO growth standards for length-for-age. This calculator uses CDC growth-chart reference data intended for children ages 2 through 20.

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