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) and can provide protection to your head if you fall and bang into the rock, although this case isn’t tested during the certification process. 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 ways to make sure a helmet fits when you try it on at the store, or to adjust your helmet that you already own. (We’ll go over each of these in detail, but want to give you a heads up of what we’ll cover.)

  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 straps
  4. Ensure the helmet is centered
  5. Adjust and close the chin strap 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, if it’s been longer since you showered, 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 adjusting each time.

For example, I (the author, Alison) have very thick hair. To keep a perfect fit during a long day of climbing, I’ll adjust (tighten) my helmet chin strap occasionally throughout the day as my hair becomes matted down. Then the next time I climb with clean/fresh hair, I have to loosen the chin strap because it’s too tight.

Head Diameter

If you can’t try helmets on in store, to ensure a helmet will fit in its most basic form, measure your head and compare it to the manufacturers specs. (On WeighMyRack, and online retailers like REI, you’ll see the head circumference listed on the product page.) To measure, wrap a flexible tape measure, or piece of cord (to measure with a non-flexible tape measure) around your forehead, just above the eyebrows and just above the ears.

About half the climbing brands who sell helmets offer 2 sizes of helmets, often stated as:

  • Small/Medium or Size 1
  • Medium/Large or Size 2

When sizing for a helmet, in addition to the size of your head/natural hair, also think about about if you’ll need room to fit a hood, hat, hijab, or would like to plan to accommodate a different hairstyle in the future. When in doubt, we recommend sizing up.

Hair note: If you have locs, braids, an afro, or just thick hair you will almost always need the larger sized helmet and even then sizing can feel too small, especially if your voluminous hair is also supported by a large head. This topic deserves a post of its own, but in the meantime, here are some IG accounts of folks we follow who have abundant hair, and who are able to find a helmet that fits.

Most the helmets in the photos above are either Black Diamond or Petzl, whose helmets come in two sizes. 

Also, if it helps, we wrote a whole post going over the largest helmet options.

We also have a filter on WeighMyRack that can help find if the helmet would fit your head diameter.

Helmet sizing filter on

Women’s vs Men’s Helmet Fit Note

For the vast majority of helmets, the only difference between “women’s” and “men’s” models is the color. (This is why on WeighMyRack we only distinguish between Adult and Kid’s helmets for fit – and not by gender).

Occasionally the women’s models also come in fewer / smaller sizes. 😠

There are only 3 helmet models that have a specific difference between the men’s and women’s version, the Petzl Borea, Petzl Meteora, and Black Diamond Half Dome Women. The difference is the women’s version has a ponytail cutout. Anybody (regardless of gender) who wears a low, centered ponytail or braid could find this feature helpful.

An extra confusing sizing conundrum: Currently all Black Diamond’s helmet models come in a Women’s version but that just means they’re only available in size S/M (and not M/L) and come in different colors. The exception is the aforementioned Half Dome Women’s model, where the women’s specific version has with a ponytail cutout (but still only comes in one size).

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 feature that holds your head in the helmet. 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 is to:

  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 or able to rattle around. A loose-fitting helmet could end up being useless depending on the type of impact.

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

Helmet webbing strap 3
Webbing straps with a plastic buckle adjustment.
helmet plastic adjustment 4
Plastic adjusters that move on both sides.
helmet dial strap 5
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 tilt your head upside down and your helmet will not easily 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. (The upside down test may not be possible to achieve with large hair/a bulky hat where the helmet sits higher on head).

Adjusting Helmet Side Straps

On the each side of the helmet, you’ll find some adjustable webbing (on most helmets). 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 and become lopsided.

This adjustment not usually a safety concern, it’s mainly for comfort.

Helmet Side Adjust - Bad - Touching Ear 6
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 7
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 8
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 front to back and side to side to make sure it fits best, and see if it feels level from all sides.

Helmets are designed to cover most of the forehead. When the fit is right, the helmet will be at the top of the head and not sitting behind the head.

A car window reflection, sunglass reflection, your phone’s camera, or feedback from your climbing partner can all be helpful to ensure the correct fit here.

This adjustment is 100% for safety. If the helmet is tilted back it not only can leave your head exposed, but any falling debris will have a more dramatic impact as the helmet will not protect you as intended. The front end of the helmet is nowhere near as strong as the top of the helmet.

Helmet too far back 9
This helmet is sitting far too back on the head and is slightly off center.
Properly centered helmet 10
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 chin strap. It’s always adjustable. Tighten it so you can easily fit one finger between the webbing and your chin. When you’re done adjusting, the strap should rest loosely against your skin. The strap should not feel like it is choking or any level of uncomfortably tight.

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 11
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 so it doesn’t flop or blow in the wind (like the helmet above), although many don’t. If the strap feels like a floppy issue, you can always add your own small rubber band to the strap to hold down the excess webbing.

We don’t recommend cutting the webbing to size, even if it is floppy. This will limit future options, as you grow your hair out, add a hat, or want to let your friend borrow you’re helmet. Most importantly, if you cut the strap you will get rid of the stopper at the end (where the webbing is folded over and sewn) that prevents the webbing from accidentally passing through the buckle – this would make it much easier for the strap to come undone and would compromise the safety of the fit.


Although this has nothing to do with fit directly, it is an important note. Today (in 2023), helmets are designed to protect your head mostly 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 for climbing certification, 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 the certified rock climbing helmet manufacturers in the world), reputable online retailers like REI, or from your trusted local outdoor retailer is the best way to ensure your helmet will keep you safe.

This post is sponsored by REI as part of a Size Inclusivity in Climbing series. In 2021 REI made an announcement that they were making a “commitment to becoming a fully inclusive, anti-racist, multicultural organization.” They followed this announcement with the Product Impact Standards, a document that specifically outlines the requirements that any partner brands they work with must meet.

By Spring of 2024, REI is requiring all apparel/gear partners to include marketing diversity and inclusive sizing as defined by these standards:

  • …have in place inclusive guidelines for marketing assets, photo casting and production that ensure diverse and inclusive representation across race, age gender identity/expression, body size/type and disability.
  • …each brand partner that sells wearable products offered in a variety of sizes to provide REI at least one sample size outside the standard size range for marketing photography.
  • …expects that all wearable products offered in a variety of sizes maintain the same price within a style regardless of size.

By Spring of 2025, they’re requiring a diverse hair type inclusion standard:

  • …each brand partner that produces headwear (helmets, hats, headbands, hoods, balaclavas, hijab, etc) to have in place guidelines for ensuring an inclusive assortment for a variety of hair types, including higher-volume and textured hair.

If you’d like to read more about how REI is fighting climate change, advancing inclusion in the outdoors, and managing chemicals, the Product Impact Standards are a great way to learn more.

Alison Dennis

Alison Dennis

Alison (she/her) runs WeighMyRack from her 17' travel trailer. She is currently touring the US and would love if you contacted her to meet up to talk about climbing, climbing gear, or if you have any fun and/or ridiculous adventure in mind.

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We’re @weighmyrack


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