Skip to content

Baby head circumference

Here is the normal head size for babies month by month, plus a calculator to see your baby’s percentile.

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).

Normal baby head circumference by month

Ranges are the WHO 2.3rd to 97.7th percentiles. The median sits roughly in the middle of each range.

  • Birth: boys 31.9 to 37.0 cm, girls 31.5 to 36.2 cm
  • 3 months: boys 38.1 to 42.9 cm, girls 37.1 to 42.0 cm
  • 6 months: boys 40.9 to 45.8 cm, girls 39.6 to 44.8 cm
  • 9 months: boys 42.5 to 47.5 cm, girls 41.2 to 46.5 cm
  • 12 months: boys 43.5 to 48.6 cm, girls 42.2 to 47.6 cm
  • 18 months: boys 44.7 to 50.0 cm, girls 43.5 to 49.0 cm
  • 24 months: boys 45.5 to 51.0 cm, girls 44.4 to 50.0 cm

Average baby head size

At birth the average is 34.5 cm for boys and 33.9 cm for girls. By 12 months it is 46.1 cm and 44.9 cm, and by 24 months 48.3 cm and 47.2 cm.

How to measure your baby’s head at home

  • Use a soft tape that does not stretch.
  • Wrap it just above the eyebrows and ears, around the widest part of the back of the head.
  • Pull it snug and read to the nearest 0.1 cm.
  • Measure three times and use the largest value.

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 a normal head circumference for a 3 month old?

About 38.1 to 42.9 cm for boys and 37.1 to 42.0 cm for girls.

What is the average baby head circumference at 6 months?

43.3 cm for boys and 42.2 cm for girls.

Does a big head mean my baby is smart?

No. Head size within the normal range tells you about growth, not intelligence.

Related charts

All charts