How to make a crochet hat the right size. It's hard to follow a pattern exactly when you are constantly using different yarn. For an adult female, the hat should fit if you crochet a circle until it measures 5 1/4" FLAT (stop your increases at that point). For a man's hat, stop you increases when your circle measures about 6 1/4" FLAT.
Katniss Cowl~ Hunter Cowl pattern on Ravelry. Yarn used in this pic is Lion Brand Wool-Ease Thick & Quick in the Granite Colorway (503) @amanda2230 Link to shawl in pic http://www.ravelry.com/projects/mandyandbingley/hunter-cowl-2