Helmet size
A helmet only protects you if it sits firm and level. Measure your head and the calculator gives you the size to start your search with.
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How the calculation works
The app maps your circumference to fixed ranges: up to 52 cm XS, up to 56 cm S, up to 59 cm M, up to 62 cm L, above that XL. These are common guide values; brand size charts can differ by a centimetre or two.
Measure with a soft tape about a finger's width above your eyebrows, level around the widest part of the back of your head.
How to read the result
Use the size as a starting point and check it against the brand's chart. If you are on a boundary, trying it on decides.
A helmet that fits already feels secure before you close the chin strap, does not slide when you shake your head and keeps your forehead covered.
Frequently asked questions
Does this work for bike and ski helmets?
The measurement is the same. Ski helmets can run smaller because of the liner, so check the model's chart and try it on with a hat or goggles.
What does a fit system do?
It usually covers several centimetres and helps if you are between two sizes or wear a thin hat in winter.
Do I need a new helmet after a crash?
After a hard impact, yes, even without visible damage. The foam inside can only absorb energy once.