You’ll find out the size(s) of any bicycle helmet on this website by checking its product description page. For instance our best selling Specialized Align helmet comes in one size: 54-62cm. This measurement corresponds with the widest part of the head that the helmet will cover. To find out your helmet size, measure your head just above eyebrow level with a tape measure as shown in this picture.
To ensure an accurate measurement, take care to wrap the tape round the head so it’s level and not tilted up or down.
One Size Bike Helmets
Thanks to economies of scale, helmets that come in one size, such as the Specialized Align, tend to be the least expensive. Thanks to their adjustable internal fit belts, one-size helmets fit most adults (and bigger kids) just fine.
Multi-size Bike Helmets
One of the reasons for considering a more expensive helmet is because it comes in a wider range of sizes. For instance the Specialized Aspire Women’s helmet comes in Small (51-57cm), Medium (54-60cm) and Large (57-63cm) so, it might offer a more accurate and snug fit.
You’ll notice these sizes cross over so if your head measures 58 or 59cm, both the medium and large size helmet will fit. If you ride through winter you might want to opt for the larger size to make more room for fitting a scull cap or hat under the helmet – just as you might wear looser fitting shoes that will accommodate thicker socks when it’s cold.