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Head circumference by age

Head size grows fast in the first year and slowly after that. Here is the typical head circumference at every age.

Head circumference percentile calculator

Sex

Enter the head circumference to see the percentile.

Data: WHO Child Growth Standards (0 to 24 months) and CDC growth charts (24 to 36 months).

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

Head circumference by age for children and adults
AgecmInchesUS
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.

How to measure your head

  1. 1 Use a soft tape measure, or a string and a ruler.
  2. 2 Wrap it around your head where the hat will sit: about 1 cm (⅜ in) above your ears and across the middle of your forehead.
  3. 3 Keep the tape level and snug, not tight. Do not pull it in.
  4. 4 Read the number where the tape overlaps. Measure two or three times and use the largest value.
  5. 5 Type the number into the calculator, or find it in the chart.
How to measure

Frequently asked questions

What is the average head circumference at 6 months?

The WHO median is 43.3 cm (17.1 in) for boys and 42.2 cm (16.6 in) for girls.

What is the average head circumference of a 5 year old?

About 50 to 52 cm (19.7 to 20.5 in).

When does head growth stop?

Most growth is finished by the late teens, when the head reaches its adult size.

Related charts

All charts