Felted hat?

I’d like to knit a hat for DH. He really would like a felted hat. I would be using Lion’sBrand Wool yarn. Any suggestions on how much bigger than usual to make it, in order to felt it to the right size?? I’ll just do the basic ribbed edge and stockinette with decreases.

Here’s a lightly felted hat pattern. Is this the kind he’s looking for?