1 month old head circumference
On the WHO growth standard, the average (median) head circumference of a 1-month-old baby boy is 37.3 cm (14.7 in) and of a girl 36.5 cm (14.4 in). The usual range, from the 3rd to the 97th percentile, is 35.1–39.5 cm for boys and 34.3–38.8 cm for girls.
Head circumference percentiles at 1 month (WHO)
The median (50th percentile) is the average head size for this age.
| 3rd | 15th | Median | 85th | 97th | |
|---|---|---|---|---|---|
| Boys (cm) | 35.1 | 36.1 | 37.3 | 38.5 | 39.5 |
| Boys (in) | 13.8 | 14.2 | 14.7 | 15.2 | 15.5 |
| Girls (cm) | 34.3 | 35.3 | 36.5 | 37.8 | 38.8 |
| Girls (in) | 13.5 | 13.9 | 14.4 | 14.9 | 15.3 |
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 1 month old’s head circumference?
WHO percentile for each head circumference, in half centimetres, at exactly 1 month. A few days older or younger shifts it slightly.
| Head | Boy | Girl |
|---|---|---|
| 34.0 cm (13.4 in) | below 1st | 1st |
| 34.5 cm (13.6 in) | below 1st | 4th |
| 35.0 cm (13.8 in) | 3rd | 9th |
| 35.5 cm (14.0 in) | 6th | 19th |
| 36.0 cm (14.2 in) | 14th | 32nd |
| 36.5 cm (14.4 in) | 25th | 48th |
| 37.0 cm (14.6 in) | 41st | 65th |
| 37.5 cm (14.8 in) | 58th | 79th |
| 38.0 cm (15.0 in) | 73rd | 89th |
| 38.5 cm (15.2 in) | 85th | 95th |
| 39.0 cm (15.4 in) | 93rd | 98th |
| 39.5 cm (15.6 in) | 97th | above 99th |
Common questions
What is the average head circumference of a 1-month-old baby?
On the WHO growth standard, the average (median) head circumference of a 1-month-old baby boy is 37.3 cm (14.7 in) and of a girl 36.5 cm (14.4 in). The usual range, from the 3rd to the 97th percentile, is 35.1–39.5 cm for boys and 34.3–38.8 cm for girls.
What percentile is a 37 cm head circumference at 1 month?
On the WHO chart, 37 cm (14.6 in) at exactly 1 month is about the 41st percentile for a boy and the 65th 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 1 month?
Going by the WHO medians, about 2.8 cm for boys and 2.7 cm for girls in the month leading up to 1 month. Head growth is fastest in the first months and slows during the second year.
Is my 1-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: 1 month old baby weight · 1 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 1 completed month. Measure around the widest part of the head, above the eyebrows and ears. For information only; not medical advice.