Yes, I'm still trying to customize hat sizes. Over the last few months, I've gotten numerous comments and questions about hats sizes. Considering we all crochet with different tensions/ gauges, it's impossible to give definite numbers of stitches. The charts are great but they do not tell us when to stop increasing. This has always been my problem with gifts. If I make something for Ireland, I'll just put it on her head and see how it fits and then adjust from there. But when you have to make a gift, it's tough to guess.
I've decided to get all of Ireland's hats that I've made for her since birth to use for my experiment. I have compared the hats to photos of her wearing them. I've looked at the dates to determine how old she was when wearing. This is how I've measured for sizes.
This is a general chart, but still pretty helpful...Better than nothing. The measurements listed in the chart represent the size of the circle you should have when increasing. When you reach the desired size then stop increasing and just crochet evenly thereafter.
Age Diameter of circle
Newborn 4 inches
3-6 months 5.5 inches
9-12 months 6-6.5 inches
24 months 6.5-6.75 inches
Toddler and small child 7 inches
Adult woman 7.25-7.5 inches
For instance if you are making a hat for a 12 month old... increase until you have a circle that measures 6-6.5 inches across, then continue to crochet each round evenly with no increases.
The hat in the photo above will be for a child about a year old. So as you can see the circle measures right at 6 inches.
The finished length will also vary according to age
Age Finished Length
Newborn 5 inches
3-6 months 6-6.5 inches
9-12 months 7 inches
24 months 7-7.5 inches
Toddler and small child 7.5- 8 inches
Adult woman 8.5-9 inches
Large adult 10 inches
The blue hat above will be for a 12 month old, so I'll need to keep crocheting for a couple more inches.
This green hat is for a teen or adult woman, so I'll stop at about 9 inches.
Edit: If you are making an ear flap hat, then the length will decrease slightly.
Of course these measurements are not exact for each child and adult. I have made hats for large adult women heads that measure more than 10 inches in length. These are general measurements intended to offer a little bit of help, instead of trying to make a hat blindly without a clue:D
I hope this helps.
Have a great week!