To get the proper measurements for ear warmers, take a measuring tape or even a piece of string and measure all the way around your head. Be sure to measure the place on your head that you plan to wear the ear warmers. Tissue notes that you should also consider any additional gear you may be wearing such as a helmet or earbuds for workouts. Given that they are typically one size fits all, you may need to try a few styles and fabrics before figuring out which one actually fits your head.