Helmets come in all kinds of different sizes and you need to fit them, just like hats. Hat sizes can be different depending on the manufacturer. The Bicycle Helmet Safety Institute (BHSI) has the most complete list of helmet sizes according to the manufacturers.
To fit a helmet you need to measure your head to find out your approximate size. Make sure you try the helmet on to make sure it fits snugly. When it is sitting on top of your head make sure it does not rock from side to side. There are sizing pads inside new models; you can use them to make sure the helmet is tucked securely on your head. Some helmets also have something called a universal sizing ring inside that can help fit the helmet on the head.
Make sure the helmet sits level on your head and low on the forehead which means that it is sitting one or two finger widths above your eyebrows.
You can center the left buckle under the chin by pulling it from the back of the helmet to lengthen or shorten the chin straps. You can do this most precisely when the helmet is off the head. There are sliders on both straps; make sure you tighten them so the fit is quite snug. A good fit is attained when you can fit no more than one or two fingers under the strap.
To find out if the helmet is fitting right give a big yawn. While you are doing this the helmet should pull down on the head. If it is not then you have to go back and tighten the chin strap even more.
If your helmet rocks back and forth on the top of your head then you might want to shorten the front strap by moving the slider forward. To prevent the buckle on the band from slipping be sure to roll it as close as you can to the band.
Helmets can be damaged if you drop them. Be sure to replace any helmet that has been damaged.
If you are buying for a kid do not buy a helmet that will be â€œgrown into.â€ The helmet must fit like it is.
The helmet should fit now. Buy a helmet that fits your head now, not a helmet to â€œgrow into.â€ Replace any helmet that has been outgrown immediately so your child or you are never riding without one.
Remember â€¦ a helmet will only be of use to you if it actually fits your head.