Ultraboost 1.0 sizing: true to size, half up if wide

Fit depth guide

Ultraboost 1.0 is a sock-fit runner/lifestyle hybrid. Length usually matches your normal Adidas size. The Primeknit upper feels snug on day one and stretches; the plastic midfoot cage is what bites wide feet.

Generations differ slightly (1.0 vs later Light Boost SKUs), but the practical rule stays TTS unless you need width or thick socks. Versus Yeezy 350 V2: do not copy a half-up Yeezy habit onto Ultraboost — convert separately.

What the US 9 Adidas chart actually maps

The brand chart on this page lists 26.2 cm at US men's 9. That is the same Adidas foot-length ladder used on Gazelle and Samba OG, and this page already labels it as chart cm — not a lab internal cut. The converter offset is +0 US because length usually matches a typical street size. If your measured foot already sits on 26.2 cm, start at US 9; the chart is a label match, not a reason to half-size on length.

The fit bar stays true to size for that reason. The width note is the override: Primeknit stretches with wear, but the TPU midfoot cage does not. Half up is for wide feet or thick socks, not because labeled length is short. Break-in is listed as none — the knit gives a little; the cage will not pack out. Prefer the intended sock-like hug at true to size if your volume is average.

The wear-box maps Ultraboost US 10 to Samba OG 10 with a width caveat (Samba is often narrower at the same length) and maps Yeezy Boost 350 V2 US 10 to Ultraboost 9.5 because 350 V2 carries a +0.5 offset. Do not copy a Yeezy half-up habit onto 1.0. Women's pages use Adidas' 1-size women's→men's gap, not always 1.5.