Bicycle Helmet Sizing
Summary: A helmet sizing chart with US hat size matched up with head circumference.
To find your approximate helmet size, measure around your head just above the eyebrows and use the table below. This is an approximate chart. Manufacturers do not always use the same size labels for a given circumference, and some are creative with small/medium or medium/large labels.
In addition to sizes, helmet shapes vary among manufacturers. You will have to try the helmet on to determine if it fits the shape of your head. A helmet that is fitted and adjusted properly should feel snug but not tight, and should not move from side-to-side or front-to-back. Expect to spend a good fifteen minutes playing with fitting pads and straps to get the best fit. You will be repaid for years with a comfortable helmet. We have some advice on fitting if you need it.
Hat Circumf. Circumf. Approx.
Size (inches) (mm) Designation
XXXXS 18.11 460 Tong Ho Hsing T-29
XXS 18 1/2 470 Toddler
6 19 483
6 1/8 19 3/8 492
6 1/4 19 3/4 502
6 3/8 20 1/8 511
6 1/2 20 1/2 521
6 5/8 20 7/8 530 Small
6 3/4 21 1/4 540 Medium
6 7/8 21 5/8 550
7 22 559
7 1/8 22 3/8 568
7 1/4 22 3/4 578 Large
7 3/8 23 1/8 587
7 1/2 23 1/2 597
7 5/8 23 7/8 606
7 3/4 24 1/4 616 Largest helmets usually
available. See our page
on big heads for more.
7 7/8 24 5/8 625
8 25 635 Louis Garneau Rev
8 1/8 25 3/8 644 Met Testagrossa, Bell Triton,
Cratoni Radon, Giro Atlas II
8 1/4 25 3/4 654 Bell Kinghead
8 3/8 26 1/8 663 Vigor Duo
8 1/2 26 1/2 673
Here is a similar chart from Bell Sports, from one of their old catalogs:
Circumference Hat Size Nominal Size
(Bell's)
20-1/2"...........6-1/2 Toddler
20-3/4"...........6-5/8 Small
21-1/4"...........6-3/4 Medium
21-5/8"...........6-7/8
22"...............7
22-3/8"...........7-1/8
22-3/4"...........7-1/4 Large
23-1/8"...........7-3/8
23-1/2"...........7-1/2
23-7/8"...........7-5/8
24-1/4"...........7-3/4
24-3/4"...........7-7/8
25-7/8"...........8-1/4 Bell Kinghead
For BMX helmet manufacturers here is a page of comparative sizing that may be helpful.
This page was last revised on: August 20, 2007.
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