Fit Confidence: how we size
Updated 2026-10-16 · Sizing engine v3.2.0
A wrong size is worse than no size. So we only name a size when we have the brand's own chart and your measurement sits clearly inside one size. If we don't have the brand's chart, you're on the line between two sizes, or a measurement is missing or outside the chart, we tell you that instead and explain how to choose. We're still building this out, so treat every suggestion as a best estimate and check the product's own chart before buying.
Coverage today
All charts come from the brand's own website. We record the source link and the date we checked it, and we never fill in missing values. Anything not listed here gets "No size yet," never a guess.
| Brand | Item | Product line | Confidence | Chart source | Chart type | Also checked | Brand-stated fit / cut | Knee braces (brand-stated) | Approved Fit Reports (brand + item) |
|---|---|---|---|---|---|---|---|---|---|
| Alpinestars | Jacket (men's) | Men's apparel (all jackets) | Up to High (model or line chart); 'between sizes' near edges | alpinestars.com · checked 2026-10-16 | Body measurements, cm (also published in inches) | hips, arm, height | not stated per product on the chart page. Euro sizing; US size = Euro − 10 (from the chart) | n/a | 0 (collecting) |
| Alpinestars | Pants (men's) | Men's apparel (all pants) | Up to High (model or line chart); 'between sizes' near edges | alpinestars.com · checked 2026-10-16 | Body measurements, cm (also published in inches) | hips, thigh, inseam, height | not stated per product on the chart page. Publishes thigh circumference per size | None stated | 0 (collecting) |
| Klim | Jacket (men's) | Men's tops (general Klim chart; applies across jackets unless a product page says otherwise) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, in | hips | not stated on the general chart. Regular, Tall and Short sleeve lengths offered (sleeve 32–35 in regular; measured differently from our shoulder-to-wrist arm, so not compared) | n/a | 0 (collecting) |
| Klim | Pants (men's) | Men's bottoms, alpha sizes (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, in | hips | not stated on the general chart. Inseam 32 in regular, 34 in Tall, 30 in Short (all sizes). Numeric waist sizes 28–48 also published | None stated | 0 (collecting) |
| Klim | Suit (men's) | Men's one-piece (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, in | waist, hips | not stated. Inseam 32/34/30 in (Regular/Tall/Short) | None stated | 0 (collecting) |
| Klim | Gloves (men's) | Men's gloves (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, cm and in | — | not stated. Palm circumference; palm length also published (19.0–22.8 cm) | n/a | 0 (collecting) |
| Klim | Helmet | F3 / F3 Carbon / F3 Carbon Pro | Up to High (model or line chart); 'between sizes' near edges | klim.com · checked 2026-10-16 | Body measurements, cm (whole cm) | — | not stated. Whole-cm head ranges; multiple cheek-pad sizes available | n/a | 0 (collecting) |
| Klim | Helmet | Krios Pro (ECE/DOT and ECE) | Up to High (model or line chart); 'between sizes' near edges | klim.com · checked 2026-10-16 | Body measurements, cm (whole cm) | — | not stated. Whole-cm head ranges; multiple cheek-pad sizes available | n/a | 0 (collecting) |
| Klim | Helmet | Krios (ECE/DOT) | Up to High (model or line chart); 'between sizes' near edges | klim.com · checked 2026-10-16 | Body measurements, cm (whole cm) | — | not stated. Whole-cm head ranges; multiple cheek-pad sizes available | n/a | 0 (collecting) |
| Bell | Helmet | MX-9 Adventure | Up to High (model or line chart); 'between sizes' near edges | bellhelmets.com · checked 2026-10-16 | Body measurements, in | — | not stated. Bell's chart has gaps between some sizes; we treat a gap as 'between sizes' | n/a | 0 (collecting) |
| Dainese | Jacket (men's) | Men's jackets, standard chart (some lines use Dainese's separate 'Comfort' chart) | Up to Medium (general chart, not specific to the model) | dainesejapan.com · checked 2026-10-16 | Body measurements, cm | arm, waist | standard (Dainese also publishes a 'Comfort / relaxed' chart for some lines). Brand-stated: separate Comfort (relaxed) chart exists. Short and Tall special sizes exist | n/a | 0 (collecting) |
| Dainese | Pants (men's) | Men's pants, standard chart (some lines use the 'Comfort' chart) | Up to Medium (general chart, not specific to the model) | dainesejapan.com · checked 2026-10-16 | Body measurements, cm | hips, inseam | standard (Comfort/relaxed chart also published). Brand-stated: separate Comfort (relaxed) chart exists | None stated | 0 (collecting) |
| Sidi | Boots | All Sidi motorcycle boots | Up to High (model or line chart); 'between sizes' near edges | sidi.com · checked 2026-10-16 | Body measurements, cm | — | not stated. Heel-to-toe foot length per size | n/a | 0 (collecting) |
| Forma | Boots | All Forma boots (general chart; Forma says fit also depends on the model) | Up to Medium (general chart, not specific to the model) | formaboots.com · checked 2026-10-16 | Body measurements, mm | — | per-model fit labels on product pages (e.g. Standard / Comfort fit). Brand-stated: fit depends on the specific model | n/a | 0 (collecting) |
| Aerostich | Suit (men's) | Men's one-piece suits (R-3, Roadcrafter) | Up to High (model or line chart); 'between sizes' near edges | aerostich.com · checked 2026-10-16 | Body measurements, in and cm | — | cut to layer over street clothes (brand chart lists body sizes). Short / Regular / Long lengths chosen by height | None stated | 0 (collecting) |
| Alpinestars | Jacket | Women's apparel (Stella and other women's jackets) | Up to High (model or line chart); 'between sizes' near edges | alpinestars.com · checked 2026-10-16 | Body measurements, in (cm table also published) | chest, waist, hips | not stated per product on the chart page. Separate women's chart with bust and chest | n/a | 0 (collecting) |
| Alpinestars | Pants | Women's apparel (Stella and other women's pants) | Up to High (model or line chart); 'between sizes' near edges | alpinestars.com · checked 2026-10-16 | Body measurements, in (cm table also published) | hips | not stated per product on the chart page. Women's pant sizes US 22–40 | None stated | 0 (collecting) |
| Klim | Jacket | Women's tops (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, in and cm | waist, hips, bicep, thigh, knee, calf | not stated on the general chart. Klim publishes chest, waist, hip, shoulder, sleeve, bicep, thigh, knee and calf for women. Inseam Extra Short 26 / Short 28 / Regular 30 / Tall 32.75 in | n/a | 0 (collecting) |
| Klim | Pants | Women's bottoms, numeric sizes (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, in and cm | hips | not stated on the general chart. X-Short / Short / Regular / Tall inseams | None stated | 0 (collecting) |
| Klim | Gloves | Women's gloves (general Klim chart) | Up to Medium (general chart, not specific to the model) | klim.com · checked 2026-10-16 | Body measurements, cm and in | — | not stated. Palm circumference | n/a | 0 (collecting) |
| Dainese | Jacket | Women's jackets, standard chart (some lines use the 'Comfort' chart) | Up to Medium (general chart, not specific to the model) | dainesejapan.com · checked 2026-10-16 | Body measurements, cm | waist, arm | standard (Comfort/relaxed chart also published). Brand-stated: separate Comfort (relaxed) chart exists | n/a | 0 (collecting) |
| Dainese | Pants | Women's pants, standard chart (some lines use the 'Comfort' chart) | Up to Medium (general chart, not specific to the model) | dainesejapan.com · checked 2026-10-16 | Body measurements, cm | hips, inseam | standard (Comfort/relaxed chart also published). Brand-stated: separate Comfort (relaxed) chart exists | None stated | 0 (collecting) |
| Aerostich | Suit | Women's one-piece suits | Up to High (model or line chart); 'between sizes' near edges | aerostich.com · checked 2026-10-16 | Body measurements, in and cm | — | cut to layer over street clothes (brand chart lists body sizes). Short / Regular / Long by height range. Women's sizes 2–20 | None stated | 0 (collecting) |
Fit Report counts are live and only include reports we've reviewed and approved, never padded. Bought gear? File a Fit Report.
Brands in our deals without a usable official chart (yet)
- REV'IT!: charts are product-specific and only appear on each product page. We haven't captured the ones for current deals yet.
- Schuberth: the official pages list nominal helmet sizes (e.g. M = 57) but not head-circumference ranges, so we don't size them.
- Alpinestars gloves and boots, and Klim boots: only size-conversion tables (EU/US/JP), not body measurements.
- REV'IT! and Schuberth women's lines: not loaded, so they show "No size yet."
How a size is chosen
Women's, men's and unisex
- Pick a fit profile (men's, women's or unisex) in your account. Women's charts use bust (Alpinestars, Aerostich) or chest as the brand labels it (Klim, Dainese), plus natural waist and hips/seat.
- A women's item is only sized on that brand's women's chart. If there isn't one, you get "No size yet."
- Unisex items use the brand's unisex chart and say so. If you're on a women's profile and an item is a men's cut, we size it on the men's chart and tell you that in the result. A men's chart is never used silently.
- Helmets and most boots are unisex and use the head or foot chart.
Casual apparel and other categories
Hats, tees, hoodies, casual jackets and casual footwear only get a size when the brand publishes a body-measurement chart for that line. Otherwise they show "No size yet." The same goes for rain gear, heated gear, base layers and armor.
- We match the item's main measurement to the brand's chart for that line: chest for jackets and suits, waist for pants, head for helmets, palm circumference for gloves, foot length for boots. We look you up on the brand's chart directly, and we never add a "runs small" adjustment on top.
- Ranges are read edge to edge. Where a brand's chart leaves a gap between sizes (Bell), or lists one foot length per size (Sidi, Forma), a measurement that falls between two sizes is shown as between sizes, with advice on how to choose. Outside the chart means no size.
- Confidence is highest well inside a size on a model-specific chart. General brand charts top out at Medium.
- Proportions: where the brand publishes them, we also check hips, thigh, inseam and sleeve, and warn you, for example, "may be tight in the thigh" or "may be long in the sleeve." If you give us a measurement the brand doesn't publish (thigh, calf, knee, bicep, forearm), we say it can't be checked and lower confidence a little. A thigh that's large relative to the waist points you to relaxed or athletic cuts.
- Knee braces: if you wear braces, we only count a pants line as brace-compatible when the brand says so for your brace. None of the pants charts we've checked state brace compatibility, so we lower confidence and tell you brace fit is unverified. Rider reports are labelled with their sample size and are never presented as brand claims.
- If confidence ends up low, we show the likely size and our reasons but don't recommend it outright, and auto-buy is off.
- Deals only count as a match when the recommended size is listed in stock. Size labels are matched exactly.
New to measuring? See how to measure for motorcycle gear.
What's next
- Using approved Fit Reports to adjust confidence for each line (for example, "most riders with big thighs found it tight"), including knee-brace room
- Official charts for each product line, with source links and dates (Klim by model, Dainese, REV'IT!, Aerostich, Schuberth, Bell, Shoei, Sidi, Forma)
- Matching on more than one measurement (chest + waist + sleeve, waist + inseam), plus fit style and layering
- Boot width, helmet head shape and glove length
- Kept/returned feedback after purchase, shown in the table above
- A weekly re-check of every chart against its source
Changelog
- 2026-10-16, v3.2: Added women's charts (Alpinestars women's jackets and pants including Stella, Klim women's tops, bottoms and gloves, Dainese women's jackets and pants, Aerostich women's suits), a fit-profile setting, bust, underbust and natural-waist fields, and gear categories that mirror major retailers. Women's gear.
- 2026-10-16, v3.1: Launched Fit Reports, area-by-area fit feedback from riders. The counts above are real, approved reports only.
- 2026-10-16, v3.0: Added 23 official charts from Alpinestars, Klim, Bell, Dainese, Sidi, Forma and Aerostich. Added proportion checks (hips, thigh, inseam, sleeve), optional thigh, calf, knee, bicep, forearm and knee-brace fields, and knee-brace compatibility warnings. Charts are now chosen by model for helmets, and women's items are no longer sized with men's charts.
- 2026-10-16, v2.0: Fixed gaps between helmet, glove and boot sizes that could return the largest size. Brand adjustments now apply only to their own item type and never on top of a brand chart. Out-of-chart measurements now return no size. Removed an estimated pants chart. Added confidence levels, between-sizes guidance and strict size-label matching. One sizing engine now runs the site, accounts and our AI-agent tool, with automated tests before every release.