9 month old head circumference
On the WHO growth standard, the average (median) head circumference of a 9-month-old baby boy is 45.0 cm (17.7 in) and of a girl 43.8 cm (17.3 in). The usual range, from the 3rd to the 97th percentile, is 42.6–47.4 cm for boys and 41.4–46.3 cm for girls.
Head circumference percentiles at 9 months (WHO)
The median (50th percentile) is the average head size for this age.
| 3rd | 15th | Median | 85th | 97th | |
|---|---|---|---|---|---|
| Boys (cm) | 42.6 | 43.7 | 45.0 | 46.3 | 47.4 |
| Boys (in) | 16.8 | 17.2 | 17.7 | 18.2 | 18.6 |
| Girls (cm) | 41.4 | 42.5 | 43.8 | 45.2 | 46.3 |
| Girls (in) | 16.3 | 16.7 | 17.3 | 17.8 | 18.2 |
Check your baby’s head circumference percentile
Enter the exact date of birth for a precise result, or use the centimetre table below.
Enter a date of birth and at least one measurement to see the percentile.
What percentile is my 9 month old’s head circumference?
WHO percentile for each head circumference, in half centimetres, at exactly 9 months. A few days older or younger shifts it slightly.
| Head | Boy | Girl |
|---|---|---|
| 41.0 cm (16.1 in) | below 1st | 2nd |
| 41.5 cm (16.3 in) | below 1st | 4th |
| 42.0 cm (16.5 in) | below 1st | 8th |
| 42.5 cm (16.7 in) | 2nd | 15th |
| 43.0 cm (16.9 in) | 6th | 26th |
| 43.5 cm (17.1 in) | 12th | 40th |
| 44.0 cm (17.3 in) | 21st | 55th |
| 44.5 cm (17.5 in) | 35th | 70th |
| 45.0 cm (17.7 in) | 50th | 81st |
| 45.5 cm (17.9 in) | 65th | 90th |
| 46.0 cm (18.1 in) | 79th | 95th |
| 46.5 cm (18.3 in) | 88th | 98th |
| 47.0 cm (18.5 in) | 94th | above 99th |
| 47.5 cm (18.7 in) | 98th | above 99th |
Common questions
What is the average head circumference of a 9-month-old baby?
On the WHO growth standard, the average (median) head circumference of a 9-month-old baby boy is 45.0 cm (17.7 in) and of a girl 43.8 cm (17.3 in). The usual range, from the 3rd to the 97th percentile, is 42.6–47.4 cm for boys and 41.4–46.3 cm for girls.
What percentile is a 44 cm head circumference at 9 months?
On the WHO chart, 44 cm (17.3 in) at exactly 9 months is about the 21st percentile for a boy and the 55th percentile for a girl. The table on this page gives the percentile for every half centimetre in the usual range.
How much does head circumference grow around 9 months?
Going by the WHO medians, about 0.5 cm for boys and 0.5 cm for girls in the month leading up to 9 months. Head growth is fastest in the first months and slows during the second year.
Is my 9-month-old's head too big or too small?
A head circumference between the 3rd and the 97th percentile is within the usual range, and head size often runs in families. Pediatricians look most at the trend: talk to yours if the measurement is below the 3rd or above the 97th percentile, or if the curve crosses two of the main percentile lines between visits.
Also: 9 month old baby weight · 9 month old baby length · head circumference chart by month · about head circumference
Source: WHO Child Growth Standards, head circumference-for-age, percentiles computed from the WHO LMS tables at 9 completed months. Measure around the widest part of the head, above the eyebrows and ears. For information only; not medical advice.