Measuring your head accurately is important and ensures you get a proper fit and finish. You can use a soft tape measure (or a length of string that you will have to hold up to a tape measure/ruler) to determine the length. Place the string or tape around your head about 1/4" above your ear, across the mid-forehead, completely circling the largest area around the back of the head. *You are looking for the largest measurement that is possible where you could be potentially wearing the hat.* Hold the tape firmly, but not too firmly. Basically you need to measure your head exactly where the hat will sit. If your measurement falls between sizes, choose the next largest size.