How to Convert Shoe Sizes Between US, UK, EU, and cm Without Guessing

I once ordered a pair of running shoes from a Japanese store while sitting in Shanghai, trusted a random chart I found, and landed a full size too small. The shoes were non-returnable. That mistake taught me the one thing every shoe-size chart should say at the top but almost never does: the number on the box is a label, not a measurement. The only number that actually describes your foot is its length in millimetres, and once you anchor everything to that, cross-border shoe shopping stops being a coin flip.

This guide walks through how the US, UK, EU, and centimetre systems relate to each other, why your foot length is the reliable anchor, and how to buy shoes confidently from a store in another country.

Why foot length in cm is the real anchor

Every sizing system in the world is built backwards from one physical fact: how long your foot is. A US 9, a UK 8.5, and an EU 42.5 are all just different labels stuck onto the same foot-shaped mould. If you convert one label directly into another with a formula, small rounding errors compound and you drift half a size off. If instead you map every label back to a measured foot length and read the other labels off that same row, the conversion stays honest.

So before anything else, measure your foot. Put a sheet of paper flat against a wall, stand with your heel touching the wall, and mark the paper at the tip of your longest toe. The longest toe is not always the big toe. Measure heel-to-mark in millimetres, do it in the evening when your feet are at their largest, measure both feet, and use the larger number. That single millimetre value is what you feed into the Shoe Size Converter, and it is what makes the result trustworthy.

How the four systems actually differ

Here is what is happening under each label:

US and UK use the same underlying scale but offset from each other. A US men's size is one full number above the equivalent UK size, so a US men's 9 is a UK 8. The everyday shorthand is that US and UK differ by about half a size in casual conversation, but the precise men's offset is a full number, while women's sizing offsets differently again.
EU sizing is measured in Paris points, where one point equals two-thirds of a centimetre. That is why EU numbers climb faster and use half sizes that do not line up neatly with US or UK halves. It is a length scale, not an arbitrary index.
Centimetre (and the Japanese cm scale, plus China's mm number) is the most literal of all. China's GB/T 3293 standard uses the foot length in millimetres as the shoe number directly, so a 260 mm foot is a 260, often written as size 26. The cm column is effectively your foot length printed on the box.

Because EU is a length system and US/UK are an offset pair, you cannot reliably hop from US straight to EU with mental arithmetic. Route through the foot length instead.

A worked example: a 26 cm foot

Let me make this concrete with a real measurement. Say you measured your foot at 260 mm, which is 26 cm.

Foot length: 26.0 cm (260 mm), which is also the China number 260.
US men's: about 9.
UK: about 8 (one full number below the US men's figure).
EU: about 42.5 (260 mm in Paris points lands here, with the standard half-size rounding).
Japan: 26, because the Japanese cm scale is your foot length in centimetres.

Notice how every one of those numbers ties back to the same 26 cm row. That is the whole trick. The US 9, the UK 8, the EU 42.5, and the JP 26 are not four conversions chained together; they are four readings of one physical measurement. If a chart ever gives you numbers that do not all map back to a single foot length, the chart is wrong.

Why two brands in the same size still fit differently

Even after you nail the conversion, a Nike 42, an Adidas 42, and a Clarks 42 can fit slightly differently on the same foot. The reason is the last, the foot-shaped mould a shoe is built around. Two brands can build a "42" on lasts that differ in length and width, and a running shoe carries more toe allowance than a leather dress shoe. So a perfect conversion gets you to the right number, not necessarily the right fit.

The practical rule: use the converter to get the correct number in the target system, then check that specific brand's own size guide before you buy. Brands that quote a foot-length range in their guide are the ones you can trust most, because they are speaking the same anchored language your measurement does. For sneakers, a single chart gets you within half a size most of the time, which is usually fine. For narrow-last dress shoes or expensive purchases, prefer a seller with free returns.

Buying shoes online from another region

When you shop across borders, the failure mode is almost always picking the wrong column rather than doing the maths wrong. The most common mistake is reading a women's size against a men's row, or vice versa: for the same foot, a US women's size runs roughly 1.5 numbers larger than the US men's number. So set the wearer toggle first, every time.

A few patterns I rely on:

A US-only sneaker drop: measure your foot, set the input to foot length, type the millimetres, and read the US column. No guessing in your head.
A daigou or gift order where you only know one system: type the size you know, copy the full row, and paste it into your order notes so the seller has the cm length as a backup.
A foreign size sticker with no country marked: type it into the EU field, read off the foot length in cm, and stand the shoe against your own measured foot to sanity-check before you commit.

If you find yourself doing this kind of cross-system thinking a lot, the same idea of anchoring to a single physical unit shows up everywhere in everyday conversions. A general Unit Converter handles the centimetre-to-inch step you will hit constantly when one store quotes cm and another quotes inches, so you can keep your foot measurement consistent no matter how the listing labels it.

The takeaway

Stop converting label to label. Measure your foot once, write down the millimetre number, and treat that as the truth. Every US, UK, EU, and cm value is just a different costume on that one measurement. Do that, set the wearer column correctly, check the brand's own guide for fit, and buying shoes from a store on the other side of the planet becomes a routine decision instead of a gamble on a return policy.

Made by Toolora · Updated 2026-06-13