Average head circumference by month (0 to 24 months)
- Birth: boys 34.5 cm, girls 33.9 cm
- 3 months: boys 40.5 cm, girls 39.5 cm
- 6 months: boys 43.3 cm, girls 42.2 cm
- 9 months: boys 45.0 cm, girls 43.8 cm
- 12 months: boys 46.1 cm, girls 44.9 cm
- 18 months: boys 47.4 cm, girls 46.2 cm
- 24 months: boys 48.3 cm, girls 47.2 cm
Head circumference by age for children and adults
| Age | cm | Inches | US |
|---|---|---|---|
| Preemie | 25 – 32 | 9.8 – 12.6 | – |
| Newborn | 32 – 36 | 12.6 – 14.2 | – |
| 0 to 3 months | 35 – 40.5 | 13.8 – 15.9 | – |
| 3 to 6 months | 39.5 – 43.5 | 15.6 – 17.1 | – |
| 6 to 12 months | 42 – 47 | 16.5 – 18.5 | – |
| Toddler (1 to 2 years) | 45 – 49 | 17.7 – 19.3 | – |
| 2 to 4 years | 47.5 – 51 | 18.7 – 20.1 | – |
| 5 to 8 years | 50.5 – 53 | 19.9 – 20.9 | 6 ⅜ – 6 ⅝ |
| 9 to 12 years | 52 – 55.5 | 20.5 – 21.9 | 6 ½ – 7 |
| Teen | 54 – 58 | 21.3 – 22.8 | 6 ¾ – 7 ¼ |
| Adult woman | 53 – 59.5 | 20.9 – 23.4 | 6 ⅝ – 7 ½ |
| Adult man | 55 – 60.5 | 21.7 – 23.8 | 6 ⅞ – 7 ⅝ |
How fast does the head grow?
A baby’s head grows about 2 cm a month for the first three months, about 1 cm a month from three to six months and less than half a centimetre a month in the second year. After age three, growth slows to a few millimetres a year.