Measure your head with a soft tape around the fullest part, just above the eyebrows and ears, then match that number to the brand’s size chart for a snug, stable fit.
For the full breakdown, see our best Baseball Cap Motorcycle Helmet guide.
Getting motorcycle helmet sizing right comes down to one simple measurement and one honest reality: the chart you check matters as much as the number you get. Here’s how to measure correctly, which chart to trust, and what to do when the math doesn’t feel right.
The Tape Measure Method That Works
Harley-Davidson’s fit guide advises wrapping a soft measuring tape around the fullest part of your head. For most riders, that sits just above the ears and about a half-inch above the eyebrows — roughly where a hat would rest naturally. The tape should sit level all the way around, not tilted up or down.
Take the measurement twice to confirm, and write down the number in centimeters, since that’s what most helmet charts use.
Reading the Size Chart Correctly
Every brand sizes its helmets differently, so there is no universal motorcycle helmet size. HJC’s US chart runs from 2XS at 50–51 cm up to 5XL at 68–69 cm, with each step covering a two-centimeter range. Bell Racing’s guide covers adult sizes from 51 cm to 68 cm with several intermediate stops.
Use the size chart for the exact model you’re buying, not the chart you remember from your last helmet. Youth and adult charts are separate in some brands, so double-check which one you’re reading.
Beyond the Number: Fit Testing Still Matters
The shell shape matters. Some brands run round, others oval, and two helmets in the same nominal size can feel completely different on the same head. When you try the helmet on, it should be snug around your cheeks and forehead without creating painful pressure points.
Common Measurement Mistakes To Skip
Most sizing errors trace back to three habits. Measuring too high on the forehead or too low around the neck puts the tape anywhere but the fullest part of the head. Buying by your hat size alone skips the brand chart entirely. And assuming one size fits across all models from the same maker ignores that different helmets use different shell shapes.
If you’re shopping for a half-shell or novelty-style helmet, the same measuring rules apply. The table below shows how typical measurements map to common size ranges.
| Head Circumference | Approx. Size | Note |
|---|---|---|
| 50–51 cm | 2XS | Rare adult size; check youth charts |
| 52–53 cm | XS–S | Varies by brand |
| 54–55 cm | S–M | Common crossover zone |
| 56–57 cm | M | Most common adult range |
| 58–59 cm | L | Wide availability across brands |
| 60–61 cm | XL | Check specific model charts |
| 62 cm+ | XXL+ | Fewer models; order carefully |
Before you order, check the brand’s official sizing page for the exact model. HJC publishes its full chart with U.S. hat sizes and inch ranges, and Bell Racing lists its intermediate sizes clearly.
References & Sources
- Harley-Davidson USA. “Motorcycle Helmet Fit & Size Guide.” Details the soft-tape measurement method and comparison to size charts.
- HJC Helmets US. “Size Chart.” Lists adult sizes from 2XS to 5XL with centimeter and hat-size ranges.
- Bell Racing USA. “Size Guide.” Documents adult sizing from 51 cm to 68 cm with intermediate ranges.