Size Chart - Star Wars Imperial Officers Caps

Cap: To measure for a cap place a tape measure around your head about 1/8"
        above your ear, across the mid forehead, completely circling your head. If
        your measurement falls between sizes choose the next largest size.
                                          Size        Inches   Hat Size
Small 21-1/2"  
Large 23-1/2"7-1/2
X-Large 24-1/4"7-3/4