Why shoe sizes differ between brands
You wear a US 10 — so why does one brand feel snug and another roomy in the “same” size? Because the number on the box is a label, not a measurement. Here’s what’s really going on.
The US size is a label, not a length
There is no law that fixes how long a “US 10” shoe must be. Each brand decides for itself, and they don’t agree. The result: the same US number maps to a slightly different physical foot length from one brand to the next. The label says they match; the shoes don’t.
The same size, measured: men’s US 10
Here’s the foot length each brand actually assigns to a men’s US 10, taken straight from their own size charts. That’s a spread of about 21 mm — roughly a full size — all hiding behind the same number.
| Brand | Men’s US 10 = foot length |
|---|---|
| Crocs | 26.4 cm |
| Under Armour | 26.8 cm |
| Nike | 27.1 cm |
| Air Jordan | 27.1 cm |
| Adidas | 27.1 cm |
| Hoka | 27.1 cm |
| Reebok | 27.2 cm |
| Vans | 27.9 cm |
| New Balance | 28 cm |
| Asics | 28 cm |
| On Running | 28 cm |
| Fila | 28.5 cm |
Figures are each brand’s published foot length for a men’s US 10. Smaller number = the brand runs smaller at that label.
It’s mostly about the “last”
A last is the foot-shaped mould a shoe is built around. Every brand — and often every model — uses its own lasts, which differ in length, width, toe-box shape, instep height and heel volume. A skate shoe, a running shoe and a leather sneaker can all say “US 10” and fit completely differently because their lasts were never meant to match.
On top of that, brands grade their sizes from different starting points and in different step increments, so the gap between, say, a US 9 and US 10 isn’t identical everywhere either.
Foot length is the one number that travels
Underneath every chart is the measurement that actually matters: foot length in centimetres. It’s the same physical fact no matter whose box it’s printed on, which is why it’s the most reliable thing to convert on. Instead of chaining label-to-label (US → UK → EU), which compounds rounding errors, anchor on the foot length both brands publish and find the closest match.
Measure your foot length once, then use the cross-brand converter — it anchors on cm, so it tells you the right size in the brand you’re buying instead of trusting the label. For models that run big or small on top of that, check the fit guides.
Frequently asked questions
Is a US 10 always a US 10?
No. The US number is a label, not a measurement. Different brands build shoes on different lasts, so a men’s US 10 can fit a foot anywhere from about 27 to 27.7 cm depending on the brand. Always check the foot-length column, not just the US number.
Why does my Nike fit differently from my Adidas in the same size?
Because they are not actually the same length. Nike and Adidas assign slightly different foot lengths to the same US number, and their lasts differ in width and volume. That is why converting on foot length in cm is more reliable than trusting the label.
Which measurement should I trust?
Foot length in centimetres. Every brand size chart is ultimately built on it, so it converts cleanly between brands and regions. Measure your foot once and you can find your size anywhere.