To measure your head at home take a measuring tape around the circumference of your head at a finger's width above your ears, above your eyes, and around the widest part of the back of your head. Don't make it too tight. Also, please review product description for sizing for each brim. Brim sometimes have different crowns that effect the size. 

If you need any additional help to figure out your size, please email us at info@wearbrims.com