Head circumference for boys at 2 years
At 2 years, the median head circumference for boys on the CDC 2000 growth charts is 48.7 cm (19.2 in): half of boys this age measure less and half more. The middle half of boys, from the 25th to the 75th percentile, falls between 47.7 and 49.6 cm, a spread of 1.9 cm. The outer lines of the chart, the 3rd and 97th percentiles, sit at 46.0 and 51.3 cm.
Since 23 months, the median has risen by 0.5 cm in one month. By 3 years it reaches 49.7 cm.
For girls at 2 years the median is 47.5 cm, 1.2 cm less than for boys, which is why the charts are drawn separately by sex.
From 2 years, head circumference is read on the CDC 2000 infant charts, which run to 36 months; CDC draws the 3rd to the 97th percentile.
Reading the table: a boy at 2 years who measures 49.0 cm is at about the 59th percentile, meaning that out of 100 boys this age, about 59 measure less.
Percentiles at 2 years
Download CSV (all ages)| Percentile | z-score | Metric | Imperial |
|---|---|---|---|
| 3rd | −1.88 | 46.0 cm | 18.1 in |
| 5th | −1.64 | 46.3 cm | 18.2 in |
| 10th | −1.28 | 46.8 cm | 18.4 in |
| 25th | −0.67 | 47.7 cm | 18.8 in |
| 50th (median) | 0.00 | 48.7 cm | 19.2 in |
| 75th | +0.67 | 49.6 cm | 19.5 in |
| 90th | +1.28 | 50.5 cm | 19.9 in |
| 95th | +1.64 | 51.0 cm | 20.1 in |
| 97th | +1.88 | 51.3 cm | 20.2 in |
CDC 2000 charts draw the 3rd to the 97th percentile. Values computed with the LMS method from the published tables (retrieved 2026-10-05).