Sizing For Bicycle Helmets
& Getting a Comfortable Fit

The first step in fitting bicycle helmets is to make sure you buy the right one in the first place. Measure with the tape around your head just above the ears and level front to back. Then select the size as suggested in the table below. This is only your starting point. The reality is that you have to go to the store and try a bunch on, to find one that not only fits but is comfortable.

Then use the right number of foam pads that come with the bike helmet to create a snug fit when it is placed level on your head. The padding should exert enough force on your skin that if you twist the helmet in any direction your skin should move as well.

Use the rear stabilizer mechanism, available on most helmets to fine tune the fit around your head, not so tight though that it cuts off the circulation to your brain.

Adjust the harness and the chin strap so that the helmet cannot be knocked up away from the forehead and expose this area to a brain damaging blow. If it does lift, loosen the clips that holds the straps below your ears, shorten the front strap and retighten the clip. You may now also have to adjust the fit of the chin buckle.

Try and pry the helmet forward over your eyes by lifting from the back rim. If it moves enough to obscure your vision then shorten the back strap that wraps around the back of your ear. When you have readjusted both of these ear straps, there should be no slack and the clip should rest just below the ear lobe.

The chin buckle should lay close to the throat and not around the chin. It should be tight enough to allow for a firm fit, but not so tight that you can't open your jaw fully as if you were eating a Big Mac.

Readjust after riding with your bike helmet for awhile if you find that the straps have stretched with use.

When all the straps, buckles and foam are adjusted correctly you should not be able to twist the bike helmet more than 1" in any one direction.

Bicycle Helmet Sizing Guide:

Adult:	Head size inches	Head size cm
Small	20 - 21.75	51 - 55
Medium	22 - 22.75	55 - 59
Large	23.25 - 24.5	59 - 63
One size - Men	20.75 - 24	54 - 61
One Size - Womens	19.75 - 22.5	50 - 57
Child
Toddler/infant	18.5 - 20.5	47 - 52
S/M	20.5 - 22.5	50 - 55
Medium-Large	22.5 - 23.75	57 - 60
one size	19.25 - 22.5	50 - 57

More Information:
Bike Helmet Basics
Giro Bicycle Helmets
Bell Bicycle Helmets

Mayo clinic report on the correct way to wear a bicycle helmet

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