A size guide is not at all necessary when choosing the best bucket hat to fit your head. It may be better for you to measure your head in the comfort of your home to ensure accuracy. Identify where the hat will sit and measure around that area using a tape measure. Most often, caps sit at about half an inch above your ears and eyebrows. After taking this measurement, you can compare it with the various size guides offered by different brands. It is advised that, if your measurement falls between two sizes, you purchase the larger size.