To measure your correct helmet size, measure the circumference of your head,
like a headband, one inch above the eyebrows and above the ears.
Match inch measurement to chart.
If between sizes, choose the next larger size. Helmet should fit snugly but not overly tight.

Inches Around CM Hat Size Helmet Size 19-3/4" - 20-1/8" 50-52 6-1/4 - 6-1/2 Childs S/M 21-1/4" 53-54 6-5/8 - 6-3/4 Childs L/XL 21-1/8" 51-52 6-3/8 - 6-1/2 XX-Small 21-1/4" 53-54 6-5/8 - 6-3/4 X-Small 21-5/8" 55-56 6-7/8 - 7 Small 22-3/8" 57-58 7-1/8 - 7-1/4 Medium 23-1/8" 59-60 7-3/8 - 7-1/2 Large 23-1/2" 61-62 7-5/8 - 7-3/4 X-Large 24-1/4" 63-64 7-7/8 - 8 XX-Large 24-5/8" 65-66 8-3/8 - 8-1/2 XXX-Large