Newborn - approx 14" head circumference, approx 6" hat height
3-month - approx 15" head circumference, approx 6.5" hat height
6-month - approx 17" head circumference, approx 7" hat height
9-12 month - approx 19" head circumference, approx 7.5" hat height
Toddler - approx 20-21" head circumference, approx 8" hat height
Youth - approx 22" head circumference, approx 9" hat height
Adult small - approx 23" head circumference, approx 10" hat height
Adult large - approx 24" head circumference, approx 11" hat height
If the head is larger, see below for how to add increases!
I make these patterns in my spare time, so if I don't have the size you are looking for, hang around for awhile and I might get to it.
If you'd like to adjust it yourself, you should add increase rows, with less increases each time (For hats in double crochet the pattern of rows would go as follows:
2dc in each,
2dc dc;
2dc dc dc;
2dc dc dc dc, etc)
until the circumference is slightly less than the right measure, then at the end of the pattern add length as well.
This is a good resource for the approx measures of different hat sizes:
http://www.bevscountrycottage.
