Climbing helmets are designed and certified to protect your head from rockfall or other falling (or dropped) debris. They are also are great if you accidentally hit your head against the rock (perhaps a ledge or roof you didn’t notice). They can also provide protection to your head if you fall and bang into the rock, although this case isn’t tested during the certification process. But climbing helmets can only offer all of these protections if they are fitted correctly, so we’re here with some key fitting tips to help.

There are a few key ways to make sure a helmet fits when you try it on at the store, or to adjust your helmet that you already own.

  1. Make sure your head fits in the helmet (sometimes easier said than done)
  2. Adjust the back of the helmet
  3. Adjust the sides to fit
  4. Ensure the helmet is centered
  5. Close the chinstrap buckle

You will likely find that you need to slightly adjust the helmet to fit perfectly each time you put your helmet on. You’ll notice slight changes as your hair grows, or if it’s been longer since you showered, or had a haircut, added a hood, anything can effect the perfect fit. The perfect fit will feel better and will provide the most protection, so it is worth spending a few seconds.

Related Note: I (the author, Alison) have very thick hair. To keep a perfect fit, I often adjust my helmet strap(s) throughout a long day of climbing as my hair becomes matted down.

Head Diameter

To ensure a helmet will fit in its most basic form, measure your head and compare it to the manufacturers specs. To measure, wrap a flexible tape measure, or piece of cord around your forehead, just above the eyebrows and just above the ears.

About half the climbing brands who make helmets offer 2 sizes of helmets, often stated as Small/Medium or Size 1 option and a Medium/Large or Size 2 option.

When sizing for a helmet, also think about about if you’d have room to fit a hood or hat, or would like to plan to accommodate a larger (or smaller) hairstyle. When in doubt, we recommend sizing up.

Also, if it helps, we wrote a whole blogpost going over the options of helmets for big heads. We also have a filter on WeighMyRack that can help find if the helmet would fit your head diameter.

Women’s Helmet Fit Note

Currently, the majority of the differences between most “women’s” models are color or size range. There are only 2 helmets currently being made that have a specific difference of adding a ponytail cutout. For example, currently all Black Diamond’s helmet models come in Women’s version but that just means they’re only available in size S/M (not M/L) and come in different colors, except for the newest Half Dome model, where the women’s specific version comes with a ponytail cutout.

We also have a filter on WeighMyRack to quickly find all the helmets with a ponytail cutout.

Helmet Back Adjustment

Usually there is a knob, dial, plastic or webbing type of strap system that is the primary area that holds your head in the helmet, this is the harness of the helmet that holds your head. We wrote a blog post on helmet construction if you want to dig deeper into how the suspension system actually functions. The best way to ensure the back of the helmet fits correctly are:

  1. Open the adjustment wide
  2. Put the helmet on your on your head
  3. Move the harness system (dial / webbing / plastic adjuster) so it sits right under the part of your head that is less round (if you press and slide your hand down the back of your head, you’ll find a curve where suddenly the skull dives, this is the spot)
  4. Close the harness system to be snug. Not tight – it shouldn’t leave a mark or feel like your head is getting squeezed. It also shouldn’t be loose and rattle around. A loose-fitting helmet could end up being useless depending on the impact.

Below you’ll see a sampling of the different kinds of helmet adjustment systems.

Helmet webbing strap 2
Webbing straps with a plastic buckle adjustment.
helmet plastic adjustment 3
Plastic adjusters that move on both sides.
helmet dial strap 4
A dial adjustment that is turned left or right to loosen or tighten.

At this point, even though you have only adjusted the back of the helmet, you should be able to put your head upside down and your helmet will not fall off your head. If it falls off, the helmet is either too loose, or the helmet does not fit your head in the best way possible and it could be helpful to try other helmets.

Adjusting the Helmet Sides

On the each side of the helmet, you’ll find some adjustable webbing. You want to adjust the webbing so your ears are totally clear of the straps and there is no uncomfortable rubbing. You’ll want to make sure the straps are evenly tensioned so you don’t have a loose side, which could allow the helmet to slide out of place.

Helmet Side Adjust - Bad - Touching Ear 5
This is pre-adjustment, you'll see the strap pressing against the ear with an unequal amount of space on each side.
Helmet Side Adjust Buckle Closeup 6
You can feed the webbing straps to change which side has more (or less) webbing to create a better fit.
Helmet Side Adjust - Good - more spaced 7
After adjusting the helmet you'll see the ear is free and there is no rubbing from the strap.

Ensure the Helmet is Centered

Test the helmet by trying to slightly move it side to side to make sure it fits best, and see if it feels level from side to side as well.

Your helmet should also cover most of the forehead. When this happens the helmet will be at the top of the head and not sitting more behind the head.

You don’t need to look in a mirror – though a car window reflection can be helpful.

Helmet too far back 8
This helmet is sitting far too back on the head and is slightly off center.
Properly centered helmet 9
This is a properly centered helmet, from side to side and front to back.

Close the Helmet Buckle

Helmets only have one locking buckle, on the chinstrap. It’s always adjustable. Tighten it so you can easily fit one finger between the webbing and your chin. When you don’t have a finger sliding around, the strap should rest loosely against your skin. The strap should not feel like it is choking in any way.

Sometimes you may need to readjust the strap as the day goes on and your hair settles. Or you may want to open it up to accommodate wearing a hat or hood underneath the helmet.

Helmet with finger of space plus strap band 10
Helmet strap should fit a finger through. Also note the small band that holds the excess webbing to the left of the finger.

Some helmets have a loop or band where you can tuck the excess strap away (like the helmet above), although many don’t. If the strap feels like a floppy issue, you can always add a small rubberband on the strap to hold down the excess webbing.


Although this has nothing to do with fit directly, it is an important note. At this point, helmets are designed to protect your head most from rockfall or any other falling object (ice, a dropped piece of gear, etc). Although helmets can also protect you if you fall and crash into things (rock, ledge, tree’s, etc), side impact is not currently a requirement, although some companies are suggesting it becomes one.

We only recommend buying and using helmets that are CE and or UIAA certified. This means we do not trust most Amazon-only brands. Buying only the brands you see on WeighMyRack (all certified rock climbing helmet manufacturers in the world), or from your local retailer is the best way to ensure your helmet will keep you safe.

This is a Sponsored Post

Our How To Fit Series is generously sponsored by REI. We approached REI about this series and they were thrilled to help make it happen. All words are solely the authors and have in no way been altered because of the sponsored nature of the post. We do link directly to REI’s website for some of the products mentioned.

In regards to fit, it’s worth noting REI’s free shipping for Co-op members as well as the 1-year return policy. Members can also buy and trade in used gear.

Other articles in this series include: