What Hat Sizes Sell the Most? A Guide for Baseball Cap Brands
For men, the most popular cap sizes are between 7-1/4 and 7-3/8 (22.75 to 23 inches in head size).
For women, the common sizes are 7 to 7-1/8 (22 to 22.5 inches).
Many brands also offer One Size Fits Most (OSFM) caps, which can adjust to fit different head sizes.