Height by Age: How to Understand It

Height by age is a comparison, not one correct number. A child’s recorded height means something only beside that child’s age and sex, read against the WHO 2007 height-for-age reference. The curves show how widely the reference is spread. They are not a height to reach.

The growth charts draw those curves. This page does not replace them with a table of centimeters.

Why age and sex both belong in the question

The same height in centimeters is not the same comparison at every age. It is not the same comparison for boys and for girls. WHO publishes separate height-for-age tables, and the reference changes as age changes. Without both age and sex, the result is not the WHO height-for-age comparison.

What "by age" means here

Age in this method is completed calendar months, counted from the date of birth to the measurement date. The measurement month counts only once its day reaches the birthday day. That completed month selects one published row. The comparison does not interpolate between rows.

The rows used here run from 61 through 228 months, the published ages 5–19. Exactly 5 years is 60 completed months, which is before the table, so no percentile is shown. Exactly 19 years is month 228. One month past 19 years is outside the table, and this method does not calculate a percentile there. Whole years and months use the same count: 10 years and 0 months is 120 months.

How to look at one age on the chart

Find the age along the bottom. Height runs up the side, in centimeters. Each curve is a percentile of the reference at that age. On these charts the curves are the 3rd, 15th, 50th, 85th, and 97th. The 50th is the median, not a target. Height percentile versus average height is that distinction. How to read a growth chart walks through one plotted point.

The chart is a picture of the reference for boys or for girls. It does not already contain a private measurement.

How to compare one recorded height

The height calculator uses one WHO 2007 height-for-age row for the completed month and the recorded sex. It reports a percentile and a z-score. The height percentile page explains that result, and the height percentile article goes through the comparison in more detail. The calculator stops there. An age does not become an adult height.

Why the next measurement matters

One age is one moment. A later height, measured the same way, shows whether the child is still in a similar part of the reference or has moved relative to it. That pattern says more than any single age. The reference row still cannot see puberty, health, or a loose measurement except insofar as those have already changed the recorded height.

Common questions

Is there one correct height for an age?

No. Each age has a spread. The curves describe the WHO reference at that age. They do not name a centimeter a child is supposed to reach, and this article does not list one.

Do boys and girls share one height-by-age chart?

No. The tables are separate. Use the chart that matches the sex recorded for the measurement.

Why is there no percentile at exactly five years?

Exactly 5 years is 60 completed months. The rows used here start at 61 months. Until the next completed month, this method does not produce a percentile.

Conclusion

Read height by age as a recorded height, a completed age, and sex, set against the WHO reference. Use the charts to see the spread and the calculator to place one height. Leave adult height out of the age row.