UK vs US Shoe Sizes - How They Compare

Both the UK and the US scales grew out of the old English barleycorn system, in which one full shoe size equals a third of an inch — the historical length of a single barley grain. Because both countries inherited the same step size, the gap between any two adjacent sizes is identical on either side of the Atlantic. What differs is where each scale decides to put its zero. The UK scale and the US scale count up from slightly different starting points, and that offset is the whole reason a UK number and a US number for the same foot never quite line up.

The US system also splits men's and women's sizing into two separate ladders, each climbing from its own base, whereas the EU system sidesteps the issue entirely by measuring in Paris points. That divergence in starting points leaves a roughly half-size gap for men and a larger gap for women, which is why a single rule of thumb cannot cover both. The one constant across every system is foot length in centimetres — it is the universal anchor, and the most reliable thing to compare when a size label looks ambiguous.

For men, the conversion is mercifully simple: the US size sits about half a size above the UK size, so US ≈ UK + 0.5. A UK 8 lands at about a US 8.5, a UK 9 at about a US 9.5, and a UK 10 at about a US 10.5. The men's reference table above follows this same pattern row by row, so you can read off the exact pairing rather than rely on the rule alone. Half sizes follow the offset too — a UK 8.5 maps to roughly a US 9.

The offset holds because the men's UK and men's US scales share the same barleycorn step but begin counting from points about half a size apart. It is worth treating the result as a starting estimate rather than a guarantee: the last, the shape the shoe is built around, varies between makers, so a US 9 from one brand can feel a touch roomier or tighter than a US 9 from another. When two candidate sizes are close, compare the foot-length-in-centimetres column rather than trusting the number on the box.

Women have to add more. The US women's size runs about two sizes above the UK size, so a UK 5.5 sits at roughly a US 7.5 and a UK 4 at around a US 6. The women's table above is the authority here; because the exact gap drifts a little across the range, reading the matching row is safer than applying a flat number. If you only remember one figure, "add about two" will get you close for most women's sizes.

The gap is wider for women than for men because two separate offsets stack on top of one another. First, the women's UK and women's US scales start from different points, much as the men's scales do. Second, US women's sizing is itself pitched about one-and-a-half sizes above US men's sizing — a US women's 8.5 and a US men's 7 sit on a similar foot. Layering those two shifts together is what pushes the UK-to-US women's gap out to roughly two or more, rather than the men's tidy one. As always, the figures are approximate and lasts vary, so let foot length settle any close call.