Caleb MorganBy Caleb Morgan

Updated November 2026

A mens dirt bike helmet size chart turns one tape measurement into a shell size you can order with confidence. This guide shows you how to measure your head correctly, read the size chart, and confirm the fit once the helmet arrives. Most riders only need a soft tape and about ten minutes.

Step 1: Measure Your Head Circumference

Wrap a soft measuring tape around your head about one inch above your eyebrows and ears, keeping it level all the way around the back. Pull it snug but not tight, and read the measurement in centimeters or inches. If the number falls between two sizes, choose the smaller one, since helmet padding compresses slightly over time.

Shopping for one? See our guide: Dirt Bike Helmet Size Chart: 10 Best Helmets Compared in 2026.

Step 2: Match Your Measurement to the Chart

Manufacturers publish charts that map head circumference to a size label such as S, M, L, XL. Sizes vary by brand, so always use the chart from the specific helmet you plan to buy. Here is a typical example of how a chart is laid out:

Head circumference (inches) Typical adult men’s size
21.25 to 21.75 XS
21.75 to 22.25 S
22.25 to 22.75 M
22.75 to 23.25 L
23.25 to 23.75 XL
23.75 to 24.25 2XL

Treat this table as an illustration only. Your brand’s own chart is the one that counts.

Step 3: Check Fit Before You Ride

The Fit Test

Once the helmet is on, fasten the chin strap so it sits snugly under your chin. Grip the front edge and try to rotate it forward and back and side to side. The helmet should move with your head, not slide independently. If you can pull it off without undoing the strap, it is too loose.

Check Eyewear and Goggle Clearance

Dirt bike helmets must leave room for goggles and a neck brace if you use one. Put your goggles on with the helmet fastened and confirm the strap sits flat against your cheeks without pinching. Look at the rim of the goggle frame against the helmet’s eye port for any gaps.

Common Mistakes

  • Measuring over a hat, or measuring too loosely so the number comes out too large.
  • Buying a size up because the helmet feels tight at first. Fit should be firm and even from the start.
  • Using a chart from a different brand without checking the sizing table.
  • Ignoring pressure points on the forehead or temples, which usually signal a wrong shape rather than a wrong size.
  • Assuming a helmet that fit last year still fits, since head size can change with growth or weight shifts.

A soft fabric tape measure gives the most accurate reading for head circumference, and a rigid ruler will not wrap properly around the skull. View on Amazon

Motocross-style goggles with a flexible frame help you check fit with eyewear in place before you commit to a helmet. View on Amazon

FAQ

Should I size my helmet by head circumference or by hat size?

Use head circumference, since that is what nearly every mens dirt bike helmet size chart is built on. Hat sizes do not translate reliably between brands.

What if I am between two sizes?

Choose the smaller size, then run the fit test with the chin strap fastened. Helmet padding breaks in slightly, but a helmet that is too large can shift in a crash.

How often should I replace my helmet?

Manufacturers commonly recommend replacing a helmet after a crash or impact, and many suggest replacement every few years because materials degrade over time. Check your helmet’s guidance and consult a professional if you are unsure whether yours is still safe.

Conclusion

Measure your head above the eyebrows, match that number to your brand’s chart, and confirm the fit with the strap fastened and goggles in place. A correctly sized helmet should feel firm, even, and stable when you shake your head. Recheck your measurement if your size or head shape changes, and retire any helmet that has taken a hard hit.

Ready to choose one?

Caleb Morgan

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.