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A dirt bike helmet size chart is the fastest way to narrow your options, but it only works if you measure your head correctly and understand how helmet sizes actually fit. Most riders shop by a letter or number on a label, then wonder why a helmet feels tight across the forehead or rocks back and forth on the crown. This guide walks you through how to measure, how to read sizing charts from different brands, and how to compare ten well-established helmets so you can pick a model that fits your head shape, riding style and budget. Every pick below was chosen from manufacturer specifications, brand reputation and common owner feedback patterns. We have not tested these helmets ourselves, so always confirm fit in person or through a return-friendly retailer before you ride.
Our Top Picks
Quick Comparison
| Product | Best for | Key feature |
|---|---|---|
| Fox Racing V1 Helmet | Trail and enduro riders wanting a balanced fit | Lightweight composite shell with a sizing system that favors a snug fit |
| Bell MX-9 Adventure MIPS | Adventure and dual-sport riders | MIPS liner and a visor-friendly peak design |
| Shoei VFX-EVO | Riders who prioritize premium fit and finish | Multi-density EPS liner and a fit system that accommodates varied head shapes |
| Arai MX-V | Racers seeking a precise, custom-feeling fit | Fiberglass-based shell designed around a tight, consistent fit |
| Leatt GPX 4.5 Helmet | Riders focused on rotational impact protection | Leatt’s Turbine-style rotational liner system |
| Troy Lee Designs SE5 Helmet | Riders wanting a wide shell and good ventilation | Large intake vents and an easy-to-adjust retention system |
| Thor Sector Helmet | Budget-minded riders and beginners | Straightforward sizing and a light, ventilated shell |
| Scorpion EXO-R1 Air | Riders with an oval head shape | Carbon-fiber shell with a fit system suited to longer heads |
| HJC CS-MX II Helmet | Riders who want a well-rounded, versatile helmet | Multi-density EPS liner and a wide range of sizes |
| Fly Racing Formula CC Helmet | Riders wanting a sharp-looking, vented helmet | Adjustable ventilation and a lightweight polycarbonate-fiber shell |
Fox Racing V1 Helmet
This is a strong starting point for trail and enduro riders who want a helmet that feels secure at speed without a lot of bulk. Riders with average to slightly oval head shapes often find it fits well straight out of the box.
Key specs
- Shell: composite construction
- Sizes: XS through XXL, sized by head circumference
- Certification: DOT and ECE 22.06 (confirm the current label on the model you buy)
- Ventilation: multiple intake and exhaust ports
Pros
- Secure, stable fit at higher speeds
- Good ventilation for trail riding
- Consistent sizing that tends to match charts closely
Cons
- Can run snug for riders with wider cheeks
- Less suited to very hot climates than dedicated vented designs
Bell MX-9 Adventure MIPS
Dual-sport and adventure riders who spend long hours in the saddle will appreciate this helmet’s comfortable padding and the added rotational protection of the MIPS liner. The peak is designed to work with goggles and sun shields.
Key specs
- Liner: MIPS low-friction layer
- Sizes: S through XXL, measured in centimeters of head circumference
- Peak: adjustable, visor-friendly
- Certification: DOT and ECE (check the label on your specific unit)
Pros
- MIPS adds an extra layer of rotational impact protection
- Comfortable padding for long rides
- Good visibility with the peak design
Cons
- Heavier than minimalist motocross helmets
- Peak can add wind noise at highway speeds
Shoei VFX-EVO
Riders who want a premium fit and finish, and who are willing to pay more for a helmet with a refined liner, will find the VFX-EVO a good match. It suits a wide range of head shapes thanks to its multi-density liner.
Key specs
- Liner: multi-density EPS
- Sizes: XS through XXL, sized by head circumference
- Certification: DOT and ECE 22.06
- Shell: fiberglass-based composite
Pros
- Refined, comfortable liner with a consistent fit
- Strong brand reputation for build quality
- Good noise reduction for a motocross helmet
Cons
- Premium positioning, so it is not a budget pick
- Fit can feel snug until the liner breaks in
Arai MX-V
Racers who want a precise, almost custom-feeling fit will find this helmet appealing. Arai is known for shell shapes that follow the head closely, which suits riders who dislike shifting or pressure points.
Key specs
- Shell: fiberglass-based composite
- Sizes: multiple shell sizes, sized by head circumference
- Certification: DOT and ECE 22.06
- Liner: removable, washable
Pros
- Precise fit that many owners describe as secure
- Removable liner for easy cleaning
- Well regarded among experienced motocross riders
Cons
- Narrow shell can feel tight for wide-headed riders
- Limited color and graphic options compared with some competitors
Leatt GPX 4.5 Helmet
Riders who prioritize rotational impact protection and are comfortable with a more technical helmet design will find the GPX 4.5 worth a look. It is commonly chosen by riders who want an extra safety layer beyond standard EPS.
Key specs
- Rotational system: Leatt’s Turbine-style liner
- Sizes: XS through XXL
- Certification: DOT and ECE 22.06
- Shell: composite
Pros
- Added rotational protection layer
- Clean, modern design with good ventilation
- Sizing that suits many average head shapes
Cons
- Liner system adds some weight
- Owners with narrow heads sometimes report a loose feel
Troy Lee Designs SE5 Helmet
This helmet works well for riders who ride in warm conditions and want large vents to keep airflow moving. It is also a popular choice for riders who like a wider shell and an easy-to-adjust retention system.
Key specs
- Shell: composite with large intake vents
- Sizes: XS through XXL
- Certification: DOT and ECE 22.06
- Retention: ratchet-style strap adjustment
Pros
- Strong ventilation for hot weather
- Easy strap adjustment
- Wide shell suits fuller head shapes
Cons
- Wind noise is more noticeable than with some full-face designs
- Can feel roomy for riders with narrow heads
Thor Sector Helmet
Beginners and budget-minded riders often start with a helmet like this. It offers straightforward sizing and a light, ventilated shell without the complexity of premium liner systems.
Key specs
- Shell: composite
- Sizes: XS through XXL
- Certification: DOT (confirm ECE status on your model)
- Ventilation: multiple intake ports
Pros
- Simple, predictable sizing
- Lightweight for its class
- Good value for new riders
Cons
- Liner is less refined than premium options
- Fewer advanced safety features like rotational systems
Scorpion EXO-R1 Air
Riders with longer or oval-shaped heads frequently mention this helmet as a better fit than round-shell alternatives. The carbon-fiber shell keeps weight down while the fit system accommodates a range of head proportions.
Key specs
- Shell: carbon-fiber composite
- Sizes: XS through XXL
- Certification: DOT and ECE 22.06
- Liner: removable and washable
Pros
- Good option for oval head shapes
- Light shell for its protection level
- Removable liner aids cleaning
Cons
- Carbon construction is a premium feature
- Round-headed riders may need a different shell
HJC CS-MX II Helmet
This is a versatile, well-rounded helmet for riders who want solid protection and a broad size range without paying for top-tier features. HJC is widely available, which makes exchanges easier if sizing is off.
Key specs
- Liner: multi-density EPS
- Sizes: XS through XXL
- Certification: DOT and ECE 22.06
- Shell: composite
Pros
- Broad size range covers many head sizes
- Solid protection for everyday riding
- Good balance of comfort and cost
Cons
- Graphics and finish are less premium than top brands
- Padding can compress over time
Fly Racing Formula CC Helmet
Riders who want a sharp-looking, well-ventilated helmet will find the Formula CC a solid option. Its adjustable vents help riders tune airflow for different temperatures.
Key specs
- Shell: lightweight composite
- Sizes: XS through XXL
- Certification: DOT (verify ECE on your label)
- Ventilation: adjustable intake vents
Pros
- Adjustable ventilation for varied conditions
- Attractive graphics and finishes
- Comfortable padding for its class
Cons
- Some owners report the fit runs slightly long from front to back
- Fewer advanced safety layers than premium helmets
Buying Guide
How to Measure Your Head for a Dirt Bike Helmet Size Chart
Before you look at any dirt bike helmet size chart, measure your head. Wrap a soft tape measure around the widest part of your head, about one inch above your eyebrows and ears. Keep the tape level and snug but not tight. Write the number down in centimeters, then convert if needed. Most brands list sizes by head circumference, so this single measurement is the one that matters most. If you are between sizes, most manufacturers recommend choosing the smaller size, since EPS liners compress slightly over time.
Selection Criteria We Used
These picks were chosen on three fronts: how well the brand publishes its sizing information, the general pattern of owner feedback about fit and comfort, and whether the helmet carries current safety certifications. We did not rank these helmets by performance in a lab, and we did not test any of them ourselves.
Important Features to Look For
- Certification labels. Look for DOT and, where available, ECE 22.06 markings inside the helmet.
- Liner type. Multi-density EPS liners are common in quality dirt bike helmets. Rotational systems such as MIPS add an extra protection layer.
- Ventilation. Intake and exhaust vents matter most in warm weather. Adjustable vents add flexibility.
- Retention system. A solid chin strap and a ratchet or D-ring closure should hold the helmet in place without pinching.
- Shell shape. Round, intermediate and oval shells suit different head proportions.
Specs to Check on Any Size Chart
- Head circumference range for each size
- Whether the chart uses centimeters, inches or both
- Whether the brand recommends sizing up or down between sizes
- Shell size (sometimes listed separately from head size)
- Return policy, since fit often requires a trial
Choosing by Need
- New riders on a budget: A straightforward helmet like the Thor Sector or HJC CS-MX II keeps things simple.
- Trail and enduro riders: The Fox Racing V1 or Troy Lee Designs SE5 suit varied terrain and long days.
- Riders focused on safety layers: The Leatt GPX 4.5 and Bell MX-9 Adventure MIPS offer rotational protection.
- Riders with oval heads: The Scorpion EXO-R1 Air is frequently mentioned for a better fit on longer shapes.
- Riders seeking premium fit: The Shoei VFX-EVO and Arai MX-V are favored by riders who want a refined, precise feel.
Things to Watch Out For
- Do not rely on a size chart alone. Fit varies between brands and models.
- Avoid buying a helmet that feels tight on the first try, expecting it to stretch. EPS liners compress rather than stretch.
- Check the date of manufacture. Helmets should be replaced after a crash or after the manufacturer’s recommended service life.
- Watch for counterfeit or unlabeled helmets, especially from unfamiliar sellers.
For more on sizing principles that apply across helmet types, see Bike Helmet Buying Guide: Fit, Safety Standards and When to Replace and How to Properly Fit, Adjust, and Replace Your Bike Helmet. If you are also shopping for a bicycle helmet for other riding, Bike Helmet Types: Road, Mountain, Commuter and Kids’ Helmets explains how the designs differ.
FAQ
How do I use a dirt bike helmet size chart?
Measure the widest part of your head about one inch above your eyebrows, then find the matching head circumference range on the chart. If you fall between two sizes, many brands suggest choosing the smaller one and checking fit with the liner snug.
Should a dirt bike helmet feel tight?
A new helmet should feel firm and even across the head, with no pressure points or movement when you shake your head. Some initial snugness is normal because EPS liners settle slightly. If you feel sharp pressure or the helmet rotates, try a different size or shape.
Do brands size helmets the same way?
No. Each manufacturer uses its own head-shape model and size labels, so a medium in one brand may fit like a large in another. Always check the specific brand’s chart before ordering.
How long does a dirt bike helmet last?
Most manufacturers recommend replacing a helmet after a crash, after any significant impact, or after the service life stated in their documentation, commonly around five years from manufacture. Check the labeling and the owner’s guide for the model you own.
Is MIPS necessary in a dirt bike helmet?
MIPS is an optional rotational impact layer. It is not required for certification, but many riders choose it for added protection in angled impacts. Weigh the extra protection against any added weight or cost.
Can I buy a dirt bike helmet online without trying it on?
You can, but choose a retailer with a clear return policy and check the brand’s size chart carefully. Measure your head before ordering, and plan for a return if the fit is not right.
Should I consult a professional about helmet fit?
If you have a head injury history, a medical condition affecting your neck, or unusual head shape, consult a qualified professional or an experienced motorsports retailer before buying. They can help with fit and safety questions beyond a size chart.
Conclusion
A dirt bike helmet size chart is a useful starting point, but the best helmet is the one that fits your head shape, feels secure at speed and suits how you ride. Measure your head first, read the brand’s chart carefully, and check the certification labels. Riders who want straightforward value often start with the Thor Sector or HJC CS-MX II. Trail riders may prefer the Fox Racing V1 or Troy Lee Designs SE5. Those prioritizing rotational protection should look at the Leatt GPX 4.5 or Bell MX-9 Adventure MIPS. Riders with oval heads may find the Scorpion EXO-R1 Air a better match, while those who want a refined, premium fit will want to compare the Shoei VFX-EVO and Arai MX-V. Whatever you choose, confirm fit in person when possible and replace any helmet that has been in a crash.
