This is a general hat sizing chart designed to reach the approximate and appropriate hat size for your and yours.
To determine your hat size use a tape measure (or a string that you will wrap around your head and then measure the length). Place string or measuring tape around your head approximately 1/8″ above your ear and across the center of your forehead. Hold firmly, (adjust to determine your comfort level) . Mark string and measure or take note of measurement indicated. If your measurement falls between sizes, choose the next largest size.