Hats/Circ question

I’m going to be making a few hats with WOTA (will get Merino next time, as I heard it is softer)
For young boys/men, what size circ would you use, and does anyone have a basic pattern?

TIA!! 

I found thissimple hat calculator, but I’ve never used it, I always use this one and love it! And I found some head sizes.
Depending upon the age…I have never had to go below 16" but if you are knitting a hat for a baby you may need to go 12", although I really don’t know baby head sizes…which is why I sent the head size chart to you :wink: !!
I used 16" circs for my nephew when he was 2, if that helps any
have fun :wink:

I’d go with 16", too.