How to Measure Your Head for Helmet Size
A helmet that does not fit your head is a helmet that cannot protect you. Too loose and it can shift during impact, exposing unprotected areas. Too tight and pressure points create headaches that tempt you to ride without it. Getting the right measurement is the essential first step.
What You Need
A flexible cloth or sewing tape measure. If you do not have one, a piece of string or a phone charging cable works — wrap it around your head, mark the overlap, then measure the length against a ruler.
How to Measure
Wrap the tape measure around the widest part of your head: just above your eyebrows at the front, across the temples, and around the fullest part of the back of your skull. Pull the tape snug but not tight — you are measuring bone structure, not compressing skin. Take the measurement three times and use the largest number.
Most riders fall between 55cm (21.7 inches) for a small and 63cm (24.8 inches) for an XXL, though sizing varies by manufacturer. Always check the specific brand's size chart — a "Large" from Shoei is not the same circumference as a "Large" from AGV.
Understanding Head Shapes
Circumference alone does not determine fit. Head shapes fall into three broad categories:
Intermediate oval is the most common shape in North America — slightly longer front-to-back than side-to-side. Shoei and HJC helmets are generally designed for intermediate oval heads.
Long oval heads are noticeably narrower when viewed from above. Arai helmets, particularly the Signet-X and Regent-X, are shaped for long-oval riders.
Round oval heads are nearly as wide as they are long. AGV and Scorpion helmets tend to accommodate round-oval shapes best.
Breaking In a New Helmet
A new helmet should feel slightly tighter than comfortable. The interior foam compresses approximately half a size during the first 15–20 hours of wear. If a new helmet feels perfect in the store, it will be too loose after break-in. If it creates genuine pain or hot spots (concentrated pressure on specific skull points), try a different size or brand — no amount of break-in will fix a shape mismatch.
My measurement falls between two sizes — which do I pick?
Go with the smaller size. The liner will compress during break-in. If the smaller size creates painful pressure points, try the larger size in a different brand that may better match your head shape.
Can I adjust the fit of a helmet I already own?
Yes. Most helmets above the budget tier offer different thickness cheek pads and crown liners that can be swapped to fine-tune the fit. Shoei offers a Personal Fitting System at authorized dealers for custom pad adjustments.