Head circumference for boys at 3 years
At 3 years, the median head circumference for boys on the CDC 2000 growth charts is 49.7 cm (19.6 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 48.6 and 50.8 cm, a spread of 2.2 cm. The outer lines of the chart, the 3rd and 97th percentiles, sit at 46.4 and 52.6 cm.
Since 2 years, the median has risen by 1.0 cm over 1 year.
For girls at 3 years the median is 48.6 cm, 1.1 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 3 years who measures 50.5 cm is at about the 70th percentile, meaning that out of 100 boys this age, about 70 measure less.
Percentiles at 3 years
Download CSV (all ages)| Percentile | z-score | Metric | Imperial |
|---|---|---|---|
| 3rd | −1.88 | 46.4 cm | 18.3 in |
| 5th | −1.64 | 46.9 cm | 18.5 in |
| 10th | −1.28 | 47.5 cm | 18.7 in |
| 25th | −0.67 | 48.6 cm | 19.1 in |
| 50th (median) | 0.00 | 49.7 cm | 19.6 in |
| 75th | +0.67 | 50.8 cm | 20.0 in |
| 90th | +1.28 | 51.7 cm | 20.3 in |
| 95th | +1.64 | 52.2 cm | 20.6 in |
| 97th | +1.88 | 52.6 cm | 20.7 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).