Caleb MorganBy Caleb Morgan

Updated November 2026

A spyder bike helmet size chart tells you which helmet size matches your head circumference, and that number is the starting point for a safe fit. In this guide, you will measure your head correctly, read the size chart, and check that the helmet sits snugly and stays put once you are on the bike. Because sizing can vary between models, the final check matters as much as the measurement.

Step 1: Measure Your Head Circumference

Wrap a soft tape measure around your head about one inch above your eyebrows and ears, keeping it level all the way around. Pull it firm but not tight, and note the number where the tape overlaps. If you are between sizes, use the larger measurement and rely on the fit test in Step 3 to decide.

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

Step 2: Match Your Measurement to the Size Chart

Find your head circumference in the size chart printed by the manufacturer for the specific helmet model you are considering. Helmet sizing is not universal, so a “Medium” in one brand may not match a “Medium” in another. Always use the chart for the exact model. Spyder and other brands typically list ranges in centimeters and inches, so check which unit the chart uses before you compare numbers.

Head circumference (inches) Typical size label
20.5 to 21.5 Extra Small
21.5 to 22.5 Small
22.5 to 23.5 Medium
23.5 to 24.5 Large
24.5 to 25.5 Extra Large

Treat this table as a general pattern only. Always confirm against the chart supplied with the helmet you plan to buy.

Step 3: Check the Fit on Your Head

Once the helmet is on, check these points before you ride:

  1. The front edge should sit about one finger width above your eyebrows.
  2. The helmet should feel snug all the way around with no pressure points.
  3. Tighten the retention system until the helmet does not shift when you shake your head.
  4. Buckle the chin strap so it fits snugly, with room for one or two fingers between the strap and your chin.

If the helmet rocks forward or back, or slides when you shake your head, try a smaller size. If it causes headaches or sharp pressure, try a larger one.

Sizing Factors That Affect Your Fit

Head shape matters as much as circumference. Some helmets are built for rounder heads and others for oval heads, so two people with the same measurement can fit differently in the same model. Hair volume and any padding you add can also change the fit. Wear the riding cap or hair style you will use on the bike when you try on a helmet.

If you are buying for a child, the process is the same, but kids grow quickly and fit can change in a single season. Check fit before every ride. For guidance on younger riders, see Dirt Bike Helmet Size Chart by Age: How to Pick the Right Fit (2026).

Common Mistakes to Avoid

  • Measuring too loosely, which leads to ordering a helmet that is too big.
  • Assuming all brands use the same size labels. Always use the model-specific chart.
  • Skipping the fit test and relying only on the tag.
  • Leaving the chin strap loose, which lets the helmet move during a fall.
  • Ignoring a helmet that feels slightly tight at first. Some padding settles, but pressure points that persist usually mean the size is wrong.

A soft tape measure makes the first step far more accurate than a string and ruler. Choose one with clear inch and centimeter markings. View on Amazon

A helmet fit check is easier with a second person adjusting the straps. If you ride alone, a mirror helps you confirm the front edge position. View on Amazon

FAQ

How do I know if my spyder bike helmet is the right size?

The helmet should feel snug all the way around, sit about one finger width above your eyebrows, and stay in place when you shake your head. If it moves or causes pressure points, try a different size.

Can I use a helmet size chart from another brand?

No. Sizing differs between brands and sometimes between models. Always use the chart supplied for the exact helmet you are buying.

Should I measure before or after putting on a cap?

Measure without a cap or with the thin layer you normally ride in. Bulky hats or thick hair can change the result, so keep the measurement consistent.

Conclusion

Measure your head level above the brows and ears, match that number to the chart for your specific helmet, and then test the fit. A correctly sized helmet should feel snug, stay still, and sit low on the forehead. Recheck the fit whenever you change helmets or if a child is growing.

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.