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Dirt Bike Helmet Size Chart & Buying Tips

Dirt bike helmet size chart data is consistent across most brands. However, some brands do come in smaller or bigger than labelled. This variation can cause frustration when ordering a dirt bike helmet online. You may have worn a 56cm from one manufacturer for many years with no issues. It does not follow that a 56cm from a different brand will be correct. You may find your new helmet is too tight (the manufacturer sizes small), or too loose (the manufacturer sizes big).

In this article, we look at how to measure your head. We have written charts for sizing of motocross helmets by the manufacturer. We also look at the variation in shell designs, safety certification, and finally, give you our top tips on keeping your dirt bike helmet in good condition. You should never buy a helmet based on price or looks alone. If you buy cheap, you can expect to buy twice. Buy for the crash, not the ride. As ever, aim to purchase the best quality you can afford.

Know your head - dirt bike helmet sizing head shape

Dirt Bike Helmet Size Chart – Top Manufacturers Comparisons

The dirt bike helmet size charts below explain the various brands and their sizing. There is nothing worse than waiting for your delivery only to realise the product is a bad fit. Knowing what to look for with a brand will help you when searching.

Any helmet purchase should start with you measuring your head. Measure around your head using a cloth measuring tape. (If you don’t have a cloth tape use a string or a lace and then lay it against a tape measure or ruler).

For the most accurate results, get a friend to help. The tape (or string) should sit above your eyebrows, and loop around the back of your head. Measure at its widest point. Keep the tape or string straight.

When you have a measurement, you’re ready to use the charts below. We have built a dirt bike helmet size chart for each brand. Once you find a brand that fits, you’re likely to stick with it so take your time. Try your helmet on as soon as it arrives. Pull the helmet on carefully. You should not manage to fit a finger under the front padding, the rear padding above the neck or under the cheek pads. Next, do a roll test – the helmet should not roll front to back when you try moving it. Instead, the head will move with the helmet as though they are one.


Youth Sizing MX Helmets

Youth Motocross Helmet Sizing Chart - FOX Helmets

A decent helmet is one of the most essential pieces of kit a rider will own. Protecting your child’s head is vital. Correct sizing is critical. Kids need to be comfortable. If a helmet is too tight, this causes discomfort, distraction and could result in injury. Too loose, and the helmet will not work the way it was designed. Worst case, the helmet could even come off in an accident.

No doubt your kids will want to try on a new helmet straight away. Let them try it on. Once in place, the helmet should be snug. It will be comfortable on the crown and should push on the cheeks. Don’t worry if the cheeks feel too snug as these pads will break in after a time.

Kids Dirt Bike Helmet Size chart - Fly Helmets

Now, do the finger and roll tests, as we mentioned earlier. Over time, remember to continually monitor the helmet as kids grow quickly. Investigate any complaints of an old helmet getting tighter!

A youth helmet is designed for younger riders and is not a small adult helmet. Depending on the child, they can have a fully grown head as young as ten years old, so take care when deciding which range to buy. Go with CM, not age.

As a rule of thumb, the range of sizes considered youth is 38.4cm / 15⅛ inches right up to 54cm/ 21¼ inches. Each brand varies considerably. Let’s take a look at the range of sizes on some of our recommended brands.

Youth Dirt Bike Helmet Sizing Chart - 6D Helmets

You can find our suggestions for some of the top youth motocross helmets here. We also wrote a detailed buying guide for kids helmets.


Adult Sizing MX Helmets

Dirt Bike Helmet Sizing Chart - 6D Helmets for adults

As an adult motocross rider, you should consider buying a new helmet every two to three seasons if you are not racing, more often if you are. The wear and tear of regular racing will affect the interior padding, fit and effectiveness. If a helmet is dropped or sustains an impact in a crash, replace it straight away.

Always check the manufacturer’s guidelines when upgrading components, or refurbishing an old helmet. Shoei are known for their refurbishing service. Providing the shell has not sustained hard impact, this option can give you an extra season.

Adult dirt bike helmet size chart for Fly helmets

Treat a new helmet as you would a new pair of boots. You should break the helmet in for a while, wearing it around at home. This ensures the fit is right before you ride. If a helmet feels too loose or uncomfortably tight, then return it straight away. You are likely to qualify for a free swap if you do. Once a helmet is worn on track, you are stuck with it.


Dirt Bike Helmet Size – Shell Designs

Shoei Adult motocross helmets size chart

There are three shell options with adult helmets; round oval, intermediate oval and long oval. These refer to your head shape as all of our heads are different. Ask that same friend who measured you to take a pic of your head directly from above, or try and take a pic yourself. It’s essential to brush any hair flat, so your head shape is apparent.

Once you know your shape, you can shop specifically for those helmets which are suited to you. The most common head shape in North America is intermediate oval.

Let’s get into the adult shapes and sizes of our quality recommended helmet brands.

fox dirt bike helmet size chart

You can find our suggestions for some of the best adult dirt bike helmets here.

All sizing is for approximate guidance only. We are all different shapes, and perfect fit cannot be guaranteed when mail ordering helmets.


Dirt Bike Helmet – Safety Certification

Buying a helmet with proper accreditation means the lid will be tested and legal for certain types of riding. A helmet without certification is little more than a toy.

When entering UK races, a helmet will need to display an ACU (Auto Cycle Union) badge to show the helmet is safe to race. For European racing, the accreditation is FIM, and US racing only acknowledges SNELL.

When hobby riding, there are various helmet certifications to look out for. You should always look out for at least one safety accreditation as a minimum. Not all MX helmets are street-legal. Helmets are only street-legal in the US when carrying the DOT certification. For the UK you will need a BSI kitemark for road use. European riders will need ECE. Make sure you allow for these differences when ordering online.


Here is a summary for each safety accreditation

ACU – The Auto-Cycle Union or ACU is affiliated to the FIM, and a silver or gold badge is required for all ACU organised race events in the UK. Independent testing is carried out before helmets receive an ACU sticker in addition to statutory testing.

FIM – Similar to the ACU certification, this badge is authorised by the FIM (Fédération Internationale de Motocyclisme or International Motorcycle Federation) and grants approval for helmets recognised to have passed safety standards for official racing use.

DOT – Approved by the Department of Transportation (hence DOT) in the USA, this certification is the minimum to look out for. The DOT certification also means a motocross helmet is street-legal within the United States. A DOT badge means the helmet has undergone a series of intense, thorough testing. Buying from a reputable dealer ensures that DOT certification is genuine.

SNELL – The Snell Memorial Foundation is considered the most thorough industry testing, purely for its rigorous methods. Tests include multi-point strikes and even dissections. Technicians have far more freedom to test and identify the weakest parts of products.

SHARP – A reasonably new name in helmet certification, SHARP is unique. It gives a star rating for various points of the helmet. SHARP is not a standalone certification but instead is completed on units that already carry ECE 22.05 ratings. It is intended for European consumers to select between existing ECE products.

ECE – The ECE 22.05 is specifically for the European market. ECE testing is more thorough than DOT,  including checking things like visibility. Crash testing is always conducted in a private authorised laboratory.


Dirt Bike Helmet Care – Top Tips

Looking after your helmet is essential. You’ll want to look-the-part on the track or the trails, but also stay safe and comfortable. Sweat, dirt, moisture and grease will attack the outside of your helmet and the lining and pads. It’s crucial, therefore, to clean both in and outside of the helmet after every ride.

Always check your owners manual for recommendations. Some helmets may carry special UV coatings and therefore need special care. Be sure to remove peaks, padding and lining before starting to clean.


Top Tips for Helmet Care

1 Use soft microfibre cloths to clean the outside as this won’t scratch the shiny surface. Soak and wring out a cloth in warm water and then lay it over the top of the helmet to loosen up any dirt and debris, while you clean the lining and pads.

2 A toothbrush with soft bristles will allow you to clean in the nooks and vents of the helmet.

3 When cleaning the lining and pads use a detergent that is non-petroleum based such as baby shampoo.

4 Use warm water and never a fancy cleaning liquid or a solvent as these may damage the coating.

5 Use a quality kit bag or helmet bag when transporting your helmet.


If you stick to these guidelines, you should find that you can pick the right helmet for you. A good quality dirt bike helmet will give you a couple of seasons of riding, mishaps aside. With the right helmet, you can ride safer and with more confidence.

Have fun out there!

Martin & TeamMA