How a Bike Helmet Should Fit: A Quick & Easy 5-Step Guide

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Does your helmet fit the way it should? There’s a good chance it may not. Understanding how a bike helmet should fit is just as important as wearing one in the first place.

Head injury is by far the most significant risk posed to cyclists. Bike helmets are designed to help reduce this risk. One study found that wearing a bike helmet significantly reduced the odds of head injuries, both serious and fatal.

That said, a bike helmet that isn’t fit properly and worn correctly will fail to protect the way it was designed to. The good news is helmet fitting is quick and easy. This step-by-step guide walks you through selecting the right size bike helmet and how to adjust it to ensure the best fit.

1. Choose the Right Size Helmet

How a bike helmet should fit begins with choosing the right size. Trying one on in person is always best. When buying online, you’ll need an accurate measurement of the circumference of your head. The easiest way to do this is to use a soft tape measure. Wrap it around your head approximately one inch above your eyebrows and ears. Make sure to keep it level the entire way around. If you don’t have a soft tape measure, use a string and then measure it with a ruler.

It’s essential that you have the correct helmet size before making any adjustments. KMV Media

Helmet sizing can vary from one brand to another, so it’s important to check a brand’s fit and sizing charts before purchasing. You never want to wear a helmet that’s too big or too small. However, if you find yourself between sizes, it’s best to size down. A helmet that’s too big can be outright dangerous. It’s always better to err on the side of it being a little too snug than too loose.

2. Position the Helmet Correctly

Once on your head, the helmet should sit level with the front edge one to two finger widths above your eyebrows. This ensures maximum protection and comfort when riding.

Your helmet should fit squarely and snugly on your head. KMV Media

Additionally, it’s important to be aware of and avoid three common positioning mistakes when wearing a helmet:

Wearing it too far back on the head. Not only is this position uncomfortable, but it exposes your forehead and face. It can also reduce the helmet’s ability to stay on your head in the event of an accident.

A helmet that hasn’t been sized or adjusted properly can shift on your head. KMV Media

Wearing it too far forward. Although your forehead and face are protected, this can obstruct your vision and expose the back of your head to greater injury in an accident.

Wearing it backward. This can increase your risk of injury far more than anything else. The easiest way to tell which side is which is the back tends to be bulkier and descend lower. Most helmets have a knob for the retention system on the back as well.

Make sure the orientation of your helmet is correct before placing it on your head. KMV Media

3. Adjust the Fit

Most bike helmets come standard with a retention system that can be adjusted to fine-tune the fit. Although every brand has its own variation, it’s basically a webbing system inside the helmet with a knob on the back for tightening and loosening. If your helmet doesn’t have a retention system, it should have some other mechanism for adjusting the fit (e.g., interchangeable interior foam pads).

Your helmet’s retention system makes it easy to dial in the proper fit. KMV Media

The goal is for the helmet to be comfortably touching your head all the way around yet snug enough that it doesn’t move when you shake your head from side to side. If you have to loosen the retention system to take the helmet off, that’s a sign you have a good fit.

If you’re someone with a lot of hair, you may need to adjust your hairstyle to ensure a proper fit. For longer hair, some helmet retention systems allow ponytails to fit through the back. For those that don’t, it’s recommended to leave your hair loose or tie it back at the base of your neck.

4. Tighten the Straps

With the helmet on, start by adjusting the side straps. They should sit flat against your head and form the shape of a “V” under and slightly in front of your ears.

Make sure to remove any slack when adjusting the side straps. KMV Media

Next, buckle the chinstrap and adjust it until it’s centered under your chin. Tighten it to the point where you can still fit two fingers between the strap and the bottom of your chin. To test if you’ve tightened it enough, open your mouth wide or yawn. When doing so, the helmet should press against the top of your head. You should also feel a bit of tension in the strap without it being too restrictive.

The chin strap should be tight but comfortable. KMV Media

Lastly, after making the above adjustments, you may be left with some excess chinstrap. You can either fold the excess and tuck it into the strap keeper (the little retainer band), or you can cut it. If you choose to cut it, be sure to leave at least 1 inch (2.5cm) past the buckle.

Once finished with your adjustments, make sure to either stow or cut any remaining strap. KMV Media

5. Avoid These Mistakes

In addition to knowing how a bike helmet should fit, there are a few things you want to make sure you avoid doing to ensure good bike helmet safety.

Don’t wear a thick hat underneath your helmet. Although it might be tempting to wear a stocking cap under your helmet on a cold day, doing so will prevent the helmet from properly fitting your head. Use a beanie or ear coverings instead.

Avoid wearing anything under the helmet that prevents it from fitting your head properly. KMV Media

Don’t add extra padding or parts or make adjustments that aren’t outlined in the manufacturer’s instructions. Not only could this potentially damage the helmet, but it could compromise its ability to function correctly in an accident.

Don’t wear someone else’s helmet. This also means you should avoid buying a used helmet. Because helmets adapt to the head of the original owner, it can lead to a loose or improper fit for you.

Next Steps

Now that you understand how a bike helmet should fit, it’s time to strap one on and hit the road. If you’re new to cycling and would like some additional tips and advice, check out our cycling for beginners guide.

Frequently Asked Questions

What should I do if my bike helmet gets damaged?

If your bike helmet gets damaged or is involved in a crash, it’s important to replace it immediately. Even if there aren’t any visible signs of damage, the foam inside the helmet may have compressed or cracked. Meaning it won’t be as effective in protecting your head against a future impact.

How often should I replace my bike helmet?

Outside of a helmet being damaged or involved in a crash, the U.S. Consumer Product Safety Commission (CPSC) recommends replacing a bike helmet within five to 10 years after it was purchased. Over time, the foam in the helmet can degrade, and the helmet may no longer provide adequate protection. Additionally, a helmet should be replaced whenever it no longer fits properly.

Can I use my bike helmet for other sports?

Bike helmets are specifically designed for impacts that may occur from falling off a bike. However, a bike helmet certified by the U.S. Consumer Product Safety Commission (CPSC) may be worn for recreational in-inline skating, roller skating, or riding a kick scooter. It should NOT be used for any other type of sport or activity, regardless of the similarity to the ones just listed.

Will decorative elements affect how a bike helmet should fit?

Although decorative elements such as horns or mohawks won’t affect how the helmet fits, they can dramatically reduce the helmet’s ability to properly protect your head. These types of elements prevent the helmet’s smooth surface from sliding after an impact which can lead to an increased chance of injury.

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Hey there! I'm Michael, founder and chief editor of Bicycle Review Guru. I've been an endurance sports junkie the majority of my adult life and fell in love with the sport of cycling when training for my first Half Ironman triathlon over 10 years ago. My passion is sharing my knowledge and expertise to help you get the most out of your cycling journey.

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