Match sizes by foot length (cm), then check model fit — US labels alone can mislead across brands.
Chart match · verify brand charts(paid link)
Full converter (model + shoes you own) · Reverse: Solovair → On
Static conversion table (crawlable). Interactive tool above uses the same cm matching.
| On US | cm | Solovair US | Solovair EU |
|---|---|---|---|
| 6.0 | 23.4 | 6.0 | 39.0 |
| 6.5 | 23.9 | 6.0 | 39.0 |
| 7.0 | 24.4 | 6.5 | 39.5 |
| 7.5 | 24.9 | 7.0 | 40.5 |
| 8.0 | 25.3 | 7.5 | 41.0 |
| 8.5 | 25.8 | 8.0 | 41.5 |
| 9.0 | 26.1 | 8.5 | 42.5 |
| 9.5 | 26.6 | 9.0 | 43.0 |
| 10.0 | 27.0 | 9.5 | 43.5 |
| 10.5 | 27.4 | 10.0 | 44.5 |
| 11.0 | 27.8 | 10.5 | 45.0 |
| 11.5 | 28.3 | 11.0 | 45.5 |
| 12.0 | 28.7 | 11.5 | 46.0 |
| 13.0 | 29.6 | 13.0 | 48.0 |
On US 10 is printed at 27.0 cm; the nearest Solovair label at that length is US 9.5 (EU 43.5). On US 10.5 (27.4 cm) maps to Solovair US 10 (EU 44.5). This bridge runs the opposite direction of Nike→Salomon: the boot brand’s US number is a half smaller for the same centimeter.
That is expected when you leave a road-running last (Cloud 5, Cloudmonster, Cloudsurfer) for a welted derby (Solovair Classic 8-Eye). Running shoes are graded around socked foot length plus toe room; Solovair’s chart is a boot last with break-in, leather, and a different EU cadence. Matching 27.0 cm and then taking Solovair TTS from your On number usually leaves the boot long.
Cloud 5 is often called short/narrow (half up common); Cloudmonster is the more forgiving On last. Do not add Cloud 5’s half-up on top of this chart’s half-down without trying — you can cancel the conversion and land in the wrong boot. Start at the Solovair US the table prints, then use the derby guide for break-in rather than another length jump.
Even when charts match, lasts differ. Check these guides:
On: Cloudmonster · Cloud 5 · Cloudsurfer
Solovair: Classic 8-Eye Derby Boot
Check prices: On Solovair (paid link)
Clothes sizing uses a separate compare path.