In general, women’s hats are sized in one size fits most sizes. This means that the style is manufactured in a single size with the adaptability to suit various head sizes ranging from 21.5 inches to 22.25 inches in circumference. With that being said, actual hat sizes vary from designer to designer. Some hats will fit a smaller or bigger head depending on the style. Some hat styles will have an adjustable inner drawstring or band to keep the hat in place.