Hat Pattern Generator at knittingrecipes.com generates a hat recipe for you based on your gauge, head circumference, and whether you prefer a fitted or slouchy look. It has 10% negative ease built right into the stitch counts. This is not a tutorial, but it is a free, thorough Stockinette hat pattern with a ribbed brim customized for you every time without you having to do any math whatsoever.

This pattern is a great blank slate for any stitch pattern you might want to add to your hat. Just enter the gauge for any stitch pattern you want to use instead of Stockinette.