Proper motorcycle helmet sizing starts with a tape measure, not a chart, and the helmet should feel snug enough to move with your head.
Getting the fit right is the difference between a helmet that protects you and one that becomes a hazard in a crash. A loose helmet can roll off or block your vision; one that’s too tight causes headaches and distraction. Fortunately, measuring your head and matching it to a helmet is a straightforward process that takes about two minutes.
Measuring Your Head the Right Way
Before you look at any size chart, you need an accurate measurement of your head’s circumference. NHTSA, the National Highway Traffic Safety Administration, recommends placing a flexible measuring tape just above your eyebrows and wrapping it around the thickest point in the rear of your head. Keep the tape level and snug against your head, but don’t pull it tight enough to compress the tape or your skin.
If you don’t have a flexible tape measure, a piece of string wrapped the same way works fine—just lay it flat against a ruler afterward. Write down the measurement in centimeters, since nearly all helmet size charts use metric sizing.
Here’s what to keep in mind while measuring:
- Measure at the widest part of your head, not high on the forehead where the skull narrows.
- Take the measurement twice to confirm you’re getting a consistent number.
- If you’re between measurements, round to the nearest full centimeter.
Matching Your Measurement to a Size Chart
Once you have your head circumference in centimeters, compare it to the manufacturer’s specific size chart. Generic adult ranges look like this, though brands like Harley-Davidson and Bell publish their own charts that may differ slightly.
| Head Circumference | US Helmet Size |
|---|---|
| 53-54 cm (20.9-21.3 in) | XS |
| 55-56 cm (21.7-22.0 in) | S |
| 57-58 cm (22.4-22.8 in) | M |
| 59-60 cm (23.2-23.6 in) | L |
| 61-62 cm (24.0-24.4 in) | XL |
| 63-64 cm (24.8-25.2 in) | 2XL |
| 65-66 cm (25.6-26.0 in) | 3XL |
| 67-68 cm (26.4-26.8 in) | 4XL |
| 69-70 cm (27.2-27.6 in) | 5XL |
Size charts are starting points, not universal truths. A 59 cm head might be a large in one brand and a medium in another, because helmet shells and liner designs vary from manufacturer to manufacturer. Always consult the chart for the specific model you’re considering, not a chart you remember from a different helmet. Riders needing the largest sizes often have the fewest options on store shelves, which is why checking tested 4XL motorcycle helmet recommendations before shopping can save hours of hunting.
How a Properly Fitted Helmet Should Feel
A correctly sized helmet feels snug all around your head, with no painful pressure points. The cheek pads should press firmly against your cheeks, and the top of your head should touch the liner without the helmet feeling like it’s squeezing you. When you shake your head gently, the helmet should move with you rather than sliding independently.
Try the roll-off test with the chin strap fastened: grab the back of the helmet and try to roll it forward off your head. If it moves enough to expose your forehead or comes off entirely, it’s too loose. A properly fitted helmet shouldn’t budge more than a finger’s width in any direction. If your measurement falls between two sizes, try the smaller one first, since helmet padding compresses and breaks in over time.
A few fit details worth extra attention:
- Cheek contact: Pads should touch your cheeks firmly without causing discomfort.
- No rocking: The helmet shouldn’t shift when you move your head up and down or side to side.
- Eyebrow clearance: The bottom edge should sit about two finger-widths above your eyebrows.
Sizing Is Only Half of Safety
A properly fitted helmet is one that meets federal safety standards and carries the right certification label. NHTSA emphasizes that fit and retention matter as much as the size label, and that a helmet which rotates easily, sits too high, or creates painful pressure points is not correctly sized regardless of what the chart says.
Recheck the fit after you’ve worn the helmet for 30 to 60 minutes. Fresh padding compresses slightly, and a helmet that felt perfect in the store can loosen enough to need a different liner thickness or a smaller size. Buying for comfort rather than correct fit is the most common sizing mistake, and it’s also the most dangerous one.
For more details on fit standards and certification, NHTSA publishes official guidance on choosing the right motorcycle helmet.
FAQs
What if my head is between two helmet sizes?
Choose the smaller size first. Helmet padding compresses and molds to your head shape over the first weeks of use, so a snug fit at purchase becomes a proper fit later. A larger helmet that feels comfortable immediately will likely feel loose after the liner breaks in.
Can I use another brand’s size chart for my helmet?
No. Each manufacturer designs its own shell shapes and liner thicknesses, so the same head circumference can map to different labeled sizes across brands. Always consult the size chart for the exact model you plan to buy.
How tight should a new helmet feel?
It should feel snug and secure with even pressure across your head and cheeks. Your cheeks should puff slightly, and the helmet should not shift when you move your head. There should be no painful pressure points or hot spots anywhere.
References & Sources
- NHTSA. “Choose the Right Motorcycle Helmet.” Official guidance on measuring head circumference and selecting a federally compliant helmet.
- Harley-Davidson. “Motorcycle Helmet Fit & Size Guide.” Brand-specific sizing advice and fit-check recommendations.
- Bell Racing. “Helmet Size Guide.” Manufacturer size chart showing how head circumference maps to labeled sizes.