Motorcycle gear sizing across regions, decoded

The standard cross-region sizing answer is that EU ≈ US − 10 for jackets and EU 7–12 maps to US XS–XXL for gloves. Both are true as a starting point and useless as a buying decision, because brand-specific cut and chart offsets routinely put you a full letter size off. Klim's S maps to EU 50 — a Dainese-50 (medium) rider would order Klim S, not M. Schuberth helmets run 1cm smaller per letter than Shoei or Arai; HJC runs 1cm bigger. Gaerne boots run half a US size smaller than Sidi at the same EU number. The brand chart overrides the formula. We at ALLR track sizing across 50+ retailers for cross-border buyers; this is the playbook for getting the fit right without a return shipment.

Four sizing systems, four ways to get it wrong

Motorcycle gear uses four distinct sizing systems depending on the garment category. Knowing which system applies to which garment is the first step in cross-region shopping.

Jackets: brand offsets that override the formula

The rough formula (US ≈ EU − 10) gets you to within ±2 of the right size — but cut, fit philosophy, and per-brand chart specifics decide whether the jacket actually fits. Italian race-cut brands (Dainese, Spidi, Alpinestars leather) are designed for tall, slim sportbike riders: narrow chest, long sleeves, pre-curved arms. Northern European and American textile brands (Klim, Rukka, Held) are cut for upright adventure-touring posture: fuller chest, shorter sleeve, more room for under-layers. The same chest measurement maps to different letter sizes across these two families.

The cell highlighted in the Klim row is the table's most important data point. A rider whose Dainese size is EU 50 (medium) does not order Klim M — they order Klim S, because Klim's letter sizes step in 4 EU units rather than 2. The mismatch comes from Klim being designed for layered adventure use; the 'M' Klim is built to fit a rider already in a base layer plus a mid-layer, so the chest dimension is closer to EU 54 than EU 50.

For a complete cross-border picture including duty, VAT, and shipping math when buying these brands from Europe, see the EU→Canada or EU→United States guides — the size question and the cross-border math compound. A Klim jacket bought from a European retailer in the wrong size means an international return shipment that's typically CAD 60–80 in lost shipping cost.

The Tech-Air / D-Air sizing trap

Airbag vests and jackets introduce a sizing complication most cross-region buyers miss. The airbag bladder takes interior space — the same body measurement requires either a vest-OVER-jacket arrangement (the vest is sized to fit over your jacket) or a vest-UNDER-jacket arrangement (the vest is sized to fit your base layer; the host jacket must accommodate the bladder). Each setup has a different chart. Three things to know:

Gloves: EU numeric to US letter (and Held's coarse-sizing trap)

Glove sizing is the cleanest cross-region conversion — both EU and US measure hand circumference around the knuckles (excluding the thumb), and the mapping is reasonably stable across brands. The trap is that EU whole-number sizing is coarser than US letter sizing: Held's 'size 9' (20.3–22.9 cm) covers what Alpinestars splits between M (20.3–21.6 cm) and L (21.9–22.9 cm).

Brand-specific notes from the Held official sizing guide, Alpinestars glove charts, and Dainese glove charts: Held sells primarily in numeric sizes (some models offer half sizes — 8.5, 9.5 — most don't). Alpinestars and Dainese use letter sizing with similar increments (~1.3 cm per letter step). A buyer who is a tight Alpinestars L should look for Held 9.5 if the model offers it, or accept that Held 10 will feel slightly loose at the heel of the hand.

Boots: three competing systems and the brand offset

Boots are the most chaotic motorcycle gear category for sizing. Three systems are simultaneously in use: EU 'Paris point' (the historical European shoe scale, ~6.67 mm per size step), Mondopoint (the modern ISO foot-length-in-millimetres scale used by ski boots and some race motorcycle boots), and US Brannock (the imperial system, ~8.46 mm per ⅓ size). The conversion between these systems isn't linear, and brands offset their charts independently of the math.

Source charts: Sidi official, TCX official, Alpinestars boots, and Gaerne (via FortNine and BTO Sports retailer charts). The numbers above are EU-to-US at the same EU number. Notice: Gaerne EU 41 = US 7, while Sidi EU 41 = US 8 — Gaerne runs half a US size smaller than Sidi at the same EU number. A rider whose street shoe is US 9 buys Sidi EU 42–43, but Gaerne EU 43. Half-size availability also varies — TCX offers half sizes in both US and EU columns; Sidi's official chart implies whole EU sizes only, with half steps appearing only in the US conversion column.

If you want the most reliable cross-brand conversion, measure your bare foot length in millimetres and use the Mondopoint column as the anchor. A foot length of 270 mm is TCX EU 42 (270 mm exactly), Sidi EU 42 (265 mm chart, but 270 mm fits), and Gaerne EU 43 (~270 mm). Mondopoint is what Sidi's race boots (Mag-1, Vortice, Mag-1 Air) use internally — even though the retail sticker shows EU sizing.

Helmets: cm of circumference (and the brand letter offsets)

Helmet sizing is the cleanest in principle — head circumference in centimetres is universal — and the messiest in practice, because every brand maps cm to S/M/L letters slightly differently. A 55 cm head is solidly S in Shoei, Arai, AGV, and Alpinestars. In HJC, the same head is borderline XS (HJC S starts at 56 cm). In Schuberth, the same head is solidly S (Schuberth S starts at 54 cm). Letter shopping across helmet brands without remeasuring is the single most common cause of helmet misfit.

The bolded cells highlight the three brand-specific offset patterns that decide whether your letter purchase fits. HJC runs 1 cm bigger per letter than Shoei/Arai (HJC S starts at 56 cm vs Shoei's 55 cm). Schuberth runs 1 cm smaller per letter (Schuberth S starts at 54 cm vs Shoei's 55 cm). Bell motorcycle is the wildcard: XS opens 1 cm higher than Shoei (54–55 cm vs 53–54), the small/medium range matches Shoei, then L–XXL compress (Bell L is 58–59 cm vs Shoei's 59–60 cm). A 56 cm head: Shoei/Arai/AGV/Alpinestars = S, HJC = XS, Schuberth = M, Bell = S. A 60 cm head: Shoei/Arai/AGV/Alpinestars = L, HJC = M, Schuberth = XL, Bell = XL. The cm number is the truth; the letter is brand convention. Measure once with a soft tape just above the eyebrows and ears, write the cm number down, and shop by cm across brands.

Note that head SHAPE matters even more than head SIZE — a properly sized helmet for the wrong head shape will still create pressure points within 20 minutes of wear. See the motorcycle helmet head shapes guide for the long-oval / intermediate-oval / round-oval determination and which brands fit which.

How to measure yourself

All four measurements take a soft fabric tape measure and one minute each. Pull the tape snug but not tight, and have someone else read the number off your back where applicable.

Women's sizing notes

Women's motorcycle gear sizing is its own ecosystem. Dainese women's EU 38 = US 0 / XXS; EU 40 = US 2 / XS; EU 42 = US 4 / S — the EU↔US gap is 38, not 10 like the men's chart. For the full women's playbook (which brands genuinely re-cut vs colorway repackages, the women's helmet myth-buster, three complete women's kits with verified picks), see the women's motorcycle gear guide. Most helmet brands do not sell women-specific helmets — they rely on shell-size + cheek-pad swap to fit smaller heads. The exception is helmet brands marketing 'Stella' or 'Women' colorways that are physically identical helmets to the unisex versions; the cm-of-circumference chart still applies.

What ALLR does about it

Every product page on ALLR shows the manufacturer's size chart for that specific model and region, with the EU number, US letter (where available), and chest/hand/foot/head measurement column when the brand publishes it. Where a brand sells distinct US-spec and EU-spec versions of the same model with different size charts, we flag the variant. The catalog filters by category for cross-region browsing: /catalog/jackets, /catalog/gloves, /catalog/boots, /catalog/helmets.

Two limits we're honest about. (1) We don't simulate fit — even a perfect size-chart match can fit differently between a Dainese race jacket and a Klim adventure jacket because of cut character. The brand chart is necessary but not sufficient. (2) Per-model size variation exists within a single brand. TCX warns that 'every TCX model is developed according to specific parameters'; Sidi's race boots and touring boots use the same chart but fit differently on the foot. When in doubt on a brand-new model, check buyer reviews on the specific size for fit notes.

Sizing is the most common cause of motorcycle gear returns. Cross-border returns are expensive — typical international return shipping runs CAD 60–80, and most European retailers don't refund original shipping. We at ALLR exist to help you get the size right the first time: the per-brand chart on every PDP, the head-shape determination for helmets, and the cross-border guides for the duty + VAT + shipping math compound.

This guide is part of the motorcycle gear buying playbook — the hub is the canonical sequence across all topic-deep guides.