Stan Smith vs Ultraboost
Both are Adidas models but they fit differently: Ultraboost runs about 1 size larger than Stan Smith at the same labelled US size.
At US men's 9 on Stan Smith
If you wear Stan Smith in US 9, start with Ultraboost in US 8: go down 1 US size. The calculation keeps the same foot length anchor, about 258mm, then removes the Stan Smith fit offset (-0.5) and applies the Ultraboost fit offset (+0.25).
| Model | Recommended US | Foot mm | UK | EU | CM |
|---|---|---|---|---|---|
| Stan Smith | 9 | 258 | 7.5 | 39 | 26 |
| Ultraboost (equivalent) | 8 | 258 | 7.5 | 39 | 26 |