baby hat sizes? help?

I need advice please.

I was reading the paper today and there was an article saying that the local Salvation Army needs people to knit or crochet hats, mittens, and blankets for babies and little kids. So I thought "great, I already have lots of baby colors of yarn and I am already crocheting scarves and stuff - maybe I will make stuff for the Salvation Army"

So I started on a smallish hat - meaning it is less big than a hat I made for myself. The trouble is that I don't know how big a small child/baby head is.

Help?

Is it like a grapefruit? Is it like Marcie's head? What can I use to gauge the proper size of the hat?

I just did a search on patterns for baby hats and the three or four that I looked at didn't give a measurement just the instructions.

There are lots of sites that have free patterns. Maybe you can find one you like and just go with that.

I looked at one that was called "kitty head hugger" thinking it might be a cat. But I was wrong.