Caleb MorganBy Caleb Morgan

Updated November 2026

A bell bike helmet size chart works best when you measure your head first and then check the fit in the helmet itself. This guide walks you through measuring your head circumference, matching it to a size, and confirming that the helmet sits correctly. Most people can do the whole process in about ten minutes at home.

Measure Your Head Circumference

Bell helmets are sized by head circumference, not by age or shoe size. 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 snug but not tight, and read the measurement in centimeters or inches. If you are between two sizes, measure again at a different time of day, since head size can shift slightly.

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

Match Your Measurement to the Size Chart

Bell publishes its own sizing ranges for each helmet model, and these can differ a little from one style to another. Use the chart on the specific product page rather than a general table. The table below shows typical adult and youth ranges as a rough guide.

Helmet Size Head Circumference (approximate)
Youth XS / Kids 48–52 cm (19–20.5 in)
Small 52–56 cm (20.5–22 in)
Medium 56–59 cm (22–23.25 in)
Large 59–62 cm (23.25–24.5 in)
Extra Large 62–65 cm (24.5–25.5 in)

Check the Fit on Your Head

A correct size is only half the job. Once the helmet is on, check these points before you ride:

  1. The helmet sits level, covering your forehead about one to two finger widths above your eyebrows.
  2. The fit dial tightens evenly and the helmet does not rock side to side or front to back when you shake your head.
  3. The side straps form a V under each ear, with the buckle sitting just below your ear.
  4. You can open your mouth wide without the helmet pulling down or pinching.

If the helmet feels loose after tightening the dial fully, try the next size down. Bell manufacturer guidance generally asks riders to replace a helmet after a crash or if it shows visible damage, so a snug, consistent fit matters for both comfort and protection.

Adjust Straps and Padding for a Secure Fit

Straps are the most common source of a poor fit, even when the size is right. Adjust the slider so the buckle rests below the ear, then tighten the chin strap so you can fit one or two fingers between the strap and your chin. Padding can also be swapped on many Bell models to fine-tune the fit, but do not stack extra padding to fill a helmet that is too large.

Ride Test Before Your First Long Trip

Wear the helmet for ten to fifteen minutes around the house before a ride. Look up, look down, and turn your head to check both sides. Any hot spot or pressure point you notice now is easier to fix than on the road.

Tips and Common Mistakes

  • Measuring over hair or a thick hat, which inflates the number and leads to a helmet that is too big.
  • Buying a larger helmet to allow room for growth in an adult; a helmet should fit now.
  • Ignoring the sizing chart for the specific model and relying on a generic table.
  • Leaving the chin strap loose so the helmet shifts in a fall.
  • Keeping a helmet that has been in a crash, even if it looks undamaged.

A good measuring tape makes the first step far more accurate. Look for a soft, flexible tailor’s tape rather than a stiff metal rule.

  • Flexible sewing tape measure: Easy to wrap around the head evenly, and quick to read in centimeters or inches. View on Amazon
  • Helmet liner pads kit: Useful for fine-tuning the fit of a helmet that is slightly too roomy. View on Amazon

FAQ

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

The helmet should sit level, feel snug without pinching, and stay in place when you shake your head. If it shifts or rocks, try the next size down or adjust the fit dial first.

Should I buy a helmet that is a little big so my child can grow into it?

No. A loose helmet can move during a fall and reduce protection. Buy the size that fits now and replace it when your child outgrows it.

Can I use a bell bike helmet size chart for other brands?

Each brand uses its own sizing, so a Bell chart is not reliable for other helmets. Always measure your head and check the specific chart for the brand you are buying.

Conclusion

Measure your head circumference, match it to the Bell chart for your exact helmet model, and then check the fit with the dial, straps, and a short test wear. Take a few minutes to get this right, and your helmet will feel comfortable and stay put on every ride. If you have a medical concern about head fit or a past injury, consult a professional.

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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.