How To Fit a Motorcycle Helmet

A motorcycle helmet only protects you if it fits. A lid that is too loose can shift or lift in a crash, and a poor shape match creates pressure points that turn a great helmet into a headache on a long ride. Getting fit right comes down to two things working together: your head's circumference (the number) and your head's shape (the geometry). We carry four helmet brands: Shoei of Japan and HJC of Korea, the two fits most riders already know, plus two European makers, Suomy of Italy and NEXX of Portugal. This guide walks you through measuring and shaping, gives you all four official size charts, and tells you exactly what to expect when you cross from one brand to another.

Step 1: Measure your head

Grab a soft, flexible cloth tape measure (not a rigid steel one). Wrap it horizontally around the largest part of your head, about 1 inch (2.5 cm) above your eyebrows in front, above your ears on the sides, and around the fullest point at the back. Keep it level. Slide the tape up and down slightly and take the reading two or three times, then use the largest measurement. This is the method Shoei, HJC, Suomy, NEXX, and U.S. safety authority NHTSA all specify.

Write the number down in centimeters. This matters more than it used to: as you'll see, the letter sizes are not identical between makers, and all four brands are calibrated straight from centimeter head circumferences. Your old size in another brand is a hint, not an answer.

Step 2: Know your head shape

Two people with the exact same circumference can need different helmets, because heads aren't round, they're ovals of different proportions. The industry (and NHTSA) sorts them into three internal shapes:

• Round Oval, front to back is nearly the same as side to side (a rounder head).
• Intermediate Oval, slightly longer front to back than side to side. This is the most common shape among North American riders.
• Long Oval, clearly longer front to back, with narrower sides.

How to find yours: have a friend photograph the top of your head looking straight down, with your hair flattened, and match it against the three illustrations above.

Why European helmets "run small"

Almost every rider crossing to a modern Suomy or NEXX reports the same thing: it feels a size smaller than expected. That isn't your imagination, and it isn't a defect, it's the new safety standard. Both brands homologate to ECE 22.06 (and their race models to the FIM FRHPhe-02 standard), which added oblique and rotational impact tests. To pass, engineers use thicker EPS foam layered in multiple densities (the crushable safety liner). Because the outer shell size is fixed by aerodynamics, that extra foam can only grow inward, so the interior volume shrinks.

The practical upshot: the old advice that "a Large in 2016 is a Large in 2026" is simply out of date. Measure in centimeters and trust the chart, not the size on the label of your last helmet.

Step 3: Read the size chart

Match your centimeter measurement to the chart for the brand and model you're considering. Suomy and NEXX label the top of the range differently, so check carefully.

Shoei size chart

HJC size chart

Suomy size chart

NEXX size chart

What if I'm between two sizes?

This is where European brands flip the old reflex. Because ECE 22.06 shrinks the interior and the EPS foam is firm and does not yield, if you land right between two centimeter brackets on a Suomy or NEXX, lean to the larger size first, then snug the fit down with the adaptive cheek and crown pads (NEXX's Ergo Fit System, Suomy's layered cheek pads). Forcing yourself into the smaller shell means fighting unyielding foam on your skull. The comfort liner will always break in a little; the safety foam will not.

Step 4: The fit check

When you first put a correctly sized helmet on, it should be a bit of work to pull down past your ears, then settle in snug and even. Run through this quick check:

• Even all around. Firm, uniform contact on your forehead, sides and cheeks. No single hot spot.
• Cheeks. The cheek pads should press your cheeks (you may look slightly "chipmunk" at first, that's correct, and they relax with use).
• Skin, not slip. Put your hands on the helmet and rotate it side to side and up and down. Your skin and eyebrows should move with the helmet. If the helmet slides over your skin, it's too big.
• Shake test. Shake and nod your head briskly, the helmet should stay locked in place.
• Roll off test. With the strap fastened, try to roll the helmet forward off the back of your head. It should not come off.
• Wear it 20-30 minutes. Some pressure points only show up after a while. A red forehead line, aching temples, or ear pain mean it's the wrong size or shape, trust that, don't "tough it out."

How our four brands fit

Each brand builds to a house interior shape, which is why models within a brand tend to fit alike:

• Shoei, intermediate oval, the benchmark. The fit most riders calibrate everything else against: even pressure, plush padding, true to the centimeter chart, and consistent from model to model, so your size in one Shoei is your size in the next. If a Shoei has always felt right, you are an intermediate oval and every row of this guide is easy to read.
• HJC, intermediate oval with a touch more side room. Very close to Shoei's shape with slightly more width at the temples, which is why rounder-headed riders often land here. The RPHA race line fits snugger and sportier than the i- and C-series street lines. Note HJC's size brackets sit about a centimeter lower than everyone else's through the upper sizes, check the chart above.
• Suomy, two families. The street Speedstar 2 and Stellar 2 come from a line Suomy's own US site sold as Round Oval, the roundest fit we stock, so a strongly oval head can feel forehead pressure there. The race line (S1-XR, SR-GP Evo, TX-Pro, Track-1) descends from shells reviewers place between intermediate and long oval, and it runs about a size small. Suomy also uses a "Triangulated Fit": firm cheek pads in multiple densities that apply intentional upward pressure on the jaw to lock the helmet at speed. Out of the box the cheeks feel very snug, that's by design. If the crown fits with no forehead pressure, the cheeks are right; they yield roughly 10% as they break in. Don't mistake correct jaw pressure for a helmet that's too small.
• NEXX, intermediate oval, snug. NEXX's own fit guidance says its helmets are built on an intermediate oval head form, and retailer measurements agree across the current line (the "NEXX runs long oval" reputation belongs to the discontinued X.R2, not today's helmets). They do run snug under ECE 22.06, and a rounder head can feel temple pressure; the retro X.G30 is the one round oval outlier. NEXX builds in an Ergo Fit / Adaptive Crown system, swappable spacer pads that open up or snug down specific areas, so side pressure can often be tuned out without changing size.

Manufacturers don't publish a per model head shape, so treat these as brand tendencies, confirmed by your own fit check.

Crossing between our brands

We carry Shoei and HJC, so if your current one fits, the simplest move is staying in that brand, your size carries straight over. If you want to cross, to a European shell or between the two you know, here's what to expect.

Coming from another brand? All 29 mapped

We researched the interior head shapes of 29 helmet brands, model by model, against manufacturer statements first, then retailer measurements, then hands on review consensus. Find the helmet that already fits you below, note its shape, and it points you straight at your next one.

Brand by brand: the street majors

Arai

The only major brand that deliberately engineers and publishes multiple interior shapes. Arai states that most of its models are Intermediate Oval (Corsair-X, Contour-X, Regent-X, Ram-X, Classic-V, XD-5, VX-PRO4), while the Quantum-X is intentionally Round Oval and the Signet-X is intentionally Long Oval. Sizing runs true; fit complaints almost always trace to picking the wrong one of the three shapes, not the wrong size.

Coming from an Arai: a Corsair, Regent, or Contour head moves straight across to a Shoei RF-1400, an HJC RPHA 71, or a NEXX. A Quantum-X head should look at the Suomy Speedstar 2 or Stellar 2. A Signet-X head sits outside our intermediate lineup. The Suomy race line leans longest of anything we carry (it runs a size small, so size up), HJC's snugger RPHA shells are the next stop, and the round oval Suomy street line is the wrong direction entirely. Run the fit check for forehead pressure before you ride.

AGV

Listed intermediate oval across the range (Pista GP RR, K6 S, K3, K1 S, Streetmodular), but reviewers consistently describe the actual interior as egg shaped, wider at the back, leaning toward the round side. The Sportmodular is called out as decidedly round oval. If an AGV fits you, HJC is the closest match we carry, and a round leaning AGV head should also try the Suomy street line.

Bell

Intermediate oval across nearly the whole current lineup, race to dirt to retro, per Bell supplied retailer data. Two exceptions matter: the classic Bullitt is Round Oval and the SRT Modular is Long Oval. Coming from a Bell: Race Star, Star, or Qualifier heads map to any of our four intermediate lines; a Bullitt head belongs in the Suomy street shells; an SRT head should try HJC's RPHA line or a NEXX.

Scorpion EXO

Uniformly intermediate oval in every spec sheet and review we checked. The catch is sizing, not shape: Scorpion runs two undocumented size groups about a half size apart at the same letter, so an EXO-R1 Air Large and a Covert FX Large are not the same interior volume. Several models (AT960, XT9000) run snug at the temples out of the box. Crossover: any of our four brands at your measured centimeters, and lean on the centimeter chart, not your Scorpion letter size.

Shark

The roundest leaning major brand. Current retailer tagging splits the catalog between round oval (base Spartan, Skwal, Evo-ES, Heritage) and intermediate oval (Spartan GT, Race-R Pro, Evo-GT), with nothing tagged long oval, and reviewers call the Spartan RS one of the roundest full face helmets sold. Coming from a Shark: the Suomy street line first, then HJC. A Shark head that felt roomy at the sides may find NEXX and the Suomy race line too narrow.

Icon

Splits by generation. The legacy shells (Airflite, Airmada, Airframe Pro, original Variant and Alliance) run long oval, narrow and tight at the cheeks. The 2020s Sport Fit refresh (Airform, Elsinore, Threshold, Ultraflite, Variant Pro) moved to intermediate oval, and the Domain is a deliberate round oval outlier. Coming from an Icon: Airflite era heads fit HJC's narrower RPHA shells and NEXX naturally; Sport Fit era heads fit all four of our brands; a Domain head should start with the Suomy street line.

Sedici and Bilt

The Cycle Gear house brands, and the most common helmets riders upgrade from. Both print their shapes on their own spec sheets: Sedici's Strada full face and ADV lines are straight intermediate oval, with the Sistema modulars listed intermediate to round oval. Bilt is intermediate oval across virtually everything except the round oval Jet open face. Upgrading from either: your shape carries to any of our four brands. A Strada 3 rider stepping up lands naturally on the RF-1400 or RPHA 71; a Sistema rider moving to a premium modular should try the Neotec 3 or RPHA 91.

Schuberth

Intermediate oval through the modular and full face range (C5, E2, S3, C3 Pro), with reviewers noting the C4 generation leaned rounder, and the open face M1 line genuinely round oval. Coming from a Schuberth: the Shoei Neotec 3 and HJC RPHA 91 are the natural modular landings; an M1 head should test the Suomy street shells.

LS2

Intermediate oval house default (87 of about 100 US SKUs), with three flagged outliers: the Valiant II modular is round oval and reviewed as fitting round heads best, while the Challenger GT and Subverter EVO run long oval and narrow. Cheek pads run snug across the brand. Crossover: most LS2 heads fit all four of our brands; Valiant II owners should try the Suomy street line, Challenger GT owners the HJC RPHA shells or a NEXX.

Nolan and X-Lite

Intermediate oval across both lines, with the flagship modulars sizing true and the older single shell street lines running about a half size small. Nolan's LPC liner strap lets you shift the liner front to back, a rare tuning tool. Crossover: straight across to any of our four intermediate lines.

Simpson

Listed intermediate oval across the Bandit family with the retro M30's shape contested between sources. Sizing is genuinely inconsistent: Simpson's own copy says the Ghost Bandit runs small and the Speed Bandit runs large. One detailed review found the Mod Bandit's interior biased long and narrow with real temple pressure. Crossover: measure in centimeters and trust the chart; Ghost and Mod Bandit heads land well in HJC's narrower shells or a NEXX.

Biltwell

Splits by family: the original Gringo, Lane Splitter, and Bonanza are all round oval, while the shield equipped Gringo S, SV, and Tahoe are intermediate oval, and the ECE 22.06 versions fit snugger than the old DOT shells they replaced. Coming from a Gringo: the Suomy street line is your shape. Gringo SV and Tahoe heads fit all four of our brands.

Klim, Ruroc, MT, Airoh, Caberg, KYT, GMAX

• Klim: intermediate oval (Krios, F5), with the Krios reviewed as roomy with a roundish bias and the GT1 Expedition modular listed long oval. ADV riders coming off a Krios land well on the Hornet X2 or DS-X1.
• Ruroc: explicitly built intermediate oval by Ruroc's own guide, runs snug, most owners size up. Moves cleanly to any of our four.
• MT: intermediate oval per UK retail fit guides and broad review consensus; race models (Rapide, KRE+) run snug at cheeks and temples.
• Airoh: unusually consistent intermediate oval across street, ADV, and MX; race shells run snug, the Commander 2 relaxed.
• Caberg: intermediate with a mild round lean, and a recurring short front to back interior on its modulars that long oval heads should avoid.
• KYT: the thinnest evidence of any brand here. The only shape signal found is a single retailer describing an oval round interior. Fit check in person before relying on it.
• GMAX: genuinely inconsistent shell to shell: FF-98 intermediate, MD-04 and MX-46 round, HH-65 long. Check the specific model, not the brand.

Dirt and dual sport brands

MX helmets follow the same three shapes. Fox builds one shared intermediate oval head form across V3 RS, V3, and V1, confirmed by both Fox's copy and retailer specs. Alpinestars is intermediate oval across every Supertech and street model, with the A-Head system adding rare crown angle adjustment. 6D and O'Neal are intermediate oval across the board. Fly Racing splits by tier: the Formula line is intermediate oval, notably narrower than most MX lids, while the entry Kinetic line and Trekker run round oval. What we carry for dirt: the Shoei VFX-EVO and HJC CL-X7, both intermediate oval, plus the HJC i50; ADV riders have the Hornet X2, DS-X1, NEXX X.WED3, and X.RL.

The crossover table

Find the helmet that fit you well. The right column is where to start with us.

"If this fits you, start here", our helmets by type

Because each brand is consistent internally, your known good size in one model is a reliable starting point for another of the same brand, then confirm with that model's chart and a fit check.

Suomy

• Race full face (FIM): S1-XR (the Ducati Corse flagship), track and road racing, the tightest, most aggressive fit.
• Sport / sport touring: SR-GP Evo, TX-Pro, Track-1, carbon performance helmets for fast road and track days.
• Sport / urban (with sun visor): Speedstar 2, Stellar 2, a rounder, more accommodating fit with a drop down internal sun shield.

NEXX

• Race full face: X.R3R, the FIM homologated flagship (in X-Pro Carbon), high speed stability.
• Sport / streetfighter: X.WST3, aggressive road full face with an internal sun visor.
• Adventure / dual sport: X.WED3, peak visor, sun shield, on and off road.
• Rally: X.RL, desert/rally styling and ventilation.
• Touring: XTR, X.LifeTour, X.LifeCountry, long haul comfort and sun visors.
• Retro / cafe: X.G30, classically styled road full face.
• Urban: Y.100R, Y.100, Y.10, Y.TRAVL, lighter city and entry helmets.

Shoei

• Race full face: X-15, the flagship racer, the snuggest fit in the range.
• Street full face: RF-1400, the do-everything benchmark, and the value RF-SR.
• Sport touring (sun visor): GT-Air 3, GT-Air II.
• Modular: Neotec 3, Neotec II.
• Adventure / dual sport: Hornet X2.
• Dirt: VFX-EVO.
• Open face / cruiser: J-Cruise II, J·O, RJ Platinum-R.

HJC

• Race full face (FIM): RPHA 1N, the MotoGP-spec flagship.
• Sport full face: RPHA 12N, RPHA 12N Carbon, RPHA 12.
• Sport touring: RPHA 71, RPHA 71 Carbon, i71.
• Street full face: i70, F71, F70, C10.
• Modular: RPHA 91, RPHA 91 Carbon, i91, i90, C91.
• Adventure / dual sport: DS-X1.
• Dirt: CL-X7, i50.
• Cruiser / open face: IS-Cruiser, V60, V31.
• Youth: CL-XY (dirt), CL-Y, Y10. Plus more in the full HJC wall.

Within each brand, your size in one model is your starting size in another, but always verify against the specific model's chart, since shell breakdowns differ by line.

Fit notes by type

• Race (X-15, RPHA 1N, S1-XR, X.R3R) and the race-derived SR-GP Evo: built to fit tight for high speed stability. Snugger than a touring helmet at the same size, that's intended.
• Adventure / rally (Hornet X2, DS-X1, X.WED3, X.RL): if you ride off road with goggles, check that goggles seat cleanly in the eye port.
• Touring & sport with internal sun visor (Speedstar 2, Stellar 2, X.WST3, XTR): the sun visor cavity reshapes the front foam slightly, do the forehead pressure check with special care.
• Urban / open style (Y-series, J-Cruise II, IS-Cruiser): lighter shells and a more relaxed fit; the roll off and shake tests matter most here.
• Modular (Neotec 3, RPHA 91, i91): do every fit check with the chin bar closed and locked, that's the shape you actually ride in.

Still not sure?

If you're between sizes, between shapes, or crossing brands, measure carefully in centimeters, start with the guidance above, and use the fit check. If you'd like a hand narrowing it down for your head shape and the bike you ride, reach out to us, we'll help you dial it in.

How we sourced this guide

The fit method and safety guidance follow primary and manufacturer sources: the U.S. NHTSA helmet fit guidance, the official Shoei, HJC, Suomy, and NEXX sizing and technical data, and the ECE 22.06 / FIM FRHPhe-02 homologation standards these helmets are built to. Head shape calls for every other brand come from our own 29 brand research pass: manufacturer statements first (Arai, Icon, Ruroc, Fox, and the Cycle Gear house brands state shapes directly), then retailer measurement data, then hands on review consensus from webBikeWorld, Bennetts BikeSocial, and long running owner communities. Where evidence is thin, we say so. Shapes can change between helmet generations, so always confirm with your own fit check. Size charts and per model liners can change with model year updates, always confirm against the current chart on the specific helmet's product page before you buy, and check that product page for the exact safety certifications (DOT, ECE 22.06, and FIM where applicable) of the model you choose.