Head circumference for girls at 8 months
At 8 months, the median head circumference for girls on the WHO Child Growth Standards is 43.4 cm (17.1 in): half of girls this age measure less and half more. The middle half of girls, from the 25th to the 75th percentile, falls between 42.5 and 44.3 cm, a spread of 1.8 cm. The outer lines of the chart, the 2nd and 98th percentiles, sit at 40.7 and 46.0 cm.
Since 7 months, the median has risen by 0.5 cm in one month. By 9 months it reaches 43.8 cm. That monthly change is less than half the 2.7 cm of the first month, because growth slows steadily through the first two years.
For boys at 8 months the median is 44.5 cm, 1.2 cm more than for girls, which is why the charts are drawn separately by sex.
On the older CDC 2000 infant charts, which some clinics and websites still use before age 2, the median at 8 months is 43.5 cm. A girl exactly on the WHO median would read as about the 46th percentile there, one reason two charts can give different answers for the same head circumference.
Reading the table: a girl at 8 months who measures 44.0 cm is at about the 68th percentile, meaning that out of 100 girls this age, about 68 measure less.
Percentiles at 8 months
Download CSV (all ages)| Percentile | z-score | Metric | Imperial |
|---|---|---|---|
| 2nd | −2.00 | 40.7 cm | 16.0 in |
| 5th | −1.64 | 41.2 cm | 16.2 in |
| 10th | −1.28 | 41.7 cm | 16.4 in |
| 25th | −0.67 | 42.5 cm | 16.7 in |
| 50th (median) | 0.00 | 43.4 cm | 17.1 in |
| 75th | +0.67 | 44.3 cm | 17.4 in |
| 90th | +1.28 | 45.1 cm | 17.7 in |
| 95th | +1.64 | 45.6 cm | 17.9 in |
| 98th | +2.00 | 46.0 cm | 18.1 in |
WHO charts label z = ±2 as the 2nd and 98th percentiles (exactly 2.3rd and 97.7th), the cutoffs CDC recommends on WHO charts. Values computed with the LMS method from the published tables (retrieved 2026-10-05).