CYCle HELMET SIZe GUIDE
You'll find out the size(s) of any bicycle helmet on this website by checking its product description page. For instance, the best selling Specialized Align cycling helmet comes in three sizes: small/medium (52-56cm), medium/large (56-60cm) and extra large (59-64cm). This measurement corresponds with the widest part of the head that the bike helmet will cover. To find out your bike helmet size , measure your head circumference just above eyebrow level with a tape measure (a metal tape measure is not ideal for this) 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. Finding the right size bike helmet is especially important as this can influence the helmet's effectiveness in terms of comfortable fit and safety.
One common misconception about a mens, womens or kids bike helmet is that the chin strap is designed to keep the helmet on but it is, in fact, the adjustable bevel on the back of the helmet that tightens to ensure a snug fit. The chin strap is merely there in case the helmet does happen to slip off in an accident. The chin strap should ideally hang two finger widths below your chin.
One Size Bike Helmets
Thanks to economies of scale, helmets that come in 'one size fits all' tend to be the least expensive. Thanks to their adjustable internal fit belts, these 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 bike helmet comes in Small (51-57cm), Medium (54-60cm) and Large (57-63cm) so, it might offer a more accurate and snug fit for different head sizes and shapes. 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 bike helmet – just as you might wear looser fitting shoes that will accommodate thicker socks when it's cold.
MIPS Bike Helmets
Available for both children and adults, brands such as Specialized, Giro and Liv all make a MIPS bike helmet. If you've heard of MIPS helmets but aren't quite sure what they are, see more detail here: Here's Why You Should Consider Using a MIPS Helmet. MIPS bike helmets come with an extra layer inside the outer shell that is designed to pivot so as to reduce rotational forces in the event of an accident. Due to this, MIPS bike helmets not only protect your head, they also protect your neck and spine.
Styles of helmets
Not so much about size but about style. If you are a mountain biker, you will likely want a helmet that comes further down the back of the head to protect against impacts whereas road cyclists can choose something that does not go down as far due to the nature of the accidents that happen in each respective discipline.