On Shoe Size Guide (UK)
On fits true to size for most buyers: 72% of wearers report a true fit, 12% find it small and 16% find it large. Use the table below to convert your foot length in millimetres straight to UK, US, EU and CM sizes — the one measurement every system agrees on. Only standard (D) width is offered, so very wide feet may need to size up.
Save your size passport
Store one foot profile in this browser and reuse it across converters, brand pages and comparison tools.
Local-only by default. Share links include foot length, width and note in the URL, so use them only with people you trust.
On size conversion table
| Foot length | UK | EU | US Men | US Women | CM |
|---|---|---|---|---|---|
| 240mm | 5.5 | 36 | 6.5 | 8 | 24 |
| 250mm | 6.5 | 38 | 7.5 | 9 | 25 |
| 260mm | 7.5 | 39 | 8.5 | 10 | 26 |
| 270mm | 9 | 41 | 10 | 11.5 | 27 |
| 280mm | 10 | 42 | 11 | 12.5 | 28 |
| 290mm | 11.5 | 44 | 12.5 | 14 | 29 |
| 300mm | 12.5 | 45 | 13.5 | 15 | 30 |
EU sizes are always rounded to a whole size — there is no exact half-size equivalent, so treat the EU column as the closest honest match.
Do On Running shoes run true to size?
On Cloud models generally fit true to size; the snug heel counter is intentional for running lockdown.
How On fits
Across our data On true to size. Of wearers, 12% report it runs small, 72% true to size, and 16% large.
| Runs small | True to size | Runs large |
|---|---|---|
| 12% | 72% | 16% |
Where this data comes from
Built from 1 On record and 640 measurements. See how we calculate for how confidence is scored.
How did On fit you?
Anonymous - no account needed, no email required. Your answer feeds our fit data and helps the next buyer get the right size.