What size hat does your child need? If you’re not able to measure a child’s head directly— such as when the hat is a gift—the following lists give 50th percentile head circumferences for boys and girls at various ages. Don’t forget hairstyle can affect fit too!

Once you have determined the correct head size, add 2cm to get the right hat size.

Girls’ head circumferences

  • 1 year of age – 45cm
  • 2 years of age – 47cm
  • 3 years of age – 48.5cm
  • 4 years of age – 49.5cm
  • 5 years of age – 50cm

(Data from the World Health Organisation ‘Head circumference-for-age – GIRLS’ chart)

Boys’ head circumferences

  • 1 year of age – 46cm
  • 2 years of age – 48.5cm
  • 3 years of age – 49.5cm
  • 4 years of age – 50cm
  • 5 years of age – 51cm

(Data from World Health Organisation ‘Head circumference-for-age – BOYS’ chart)

For kids over the age of five, we’re forced to use some guesswork about sizes as I have yet to find a published study akin to the ones above with precise info on how boys’ and girls’ heads grow as they age. As the rate of growth slows with age, and girls’ heads are consistently a little smaller than boys’, we can make the following guesses:

Girls’ head circumferences 6 and over

  • 6 to 8 years of age – 52cm
  • 8 and over – 54cm

Boys’ head circumferences 6 and over

  • 6 years of age – 52cm
  • 7 and over – 54cm

Remember, the above measurements are head sizes – you must add 2cm to get the right hat size for a comfortable fit.