Shoe Size Conversion: How US, UK, EU and Japanese Sizes Actually Relate

You found the shoes you want, but the seller only lists EU sizes — or you wear a US 9 and the chart jumps straight from “8.5” to “42” with no explanation of how they line up. Shoe sizing looks like a mess of unrelated numbers, but underneath every system is the same physical fact: the length of your foot. Once you know your foot length in centimetres, every regional size is just a different way of encoding it. This guide explains how US, UK, EU, Japanese and Chinese sizes relate, why half a number matters more than you’d think, and how to measure your feet so an online conversion actually fits.

Foot length is the only real measurement

Every sizing system in the world is a code for one thing: how long your foot is, heel to longest toe. The systems disagree only on the units and the starting point of the scale.

• Japan and Mondopoint are the honest ones — the size simply is your foot length in centimetres. If your foot is 26 cm, your Japanese size is 26. This is why the Japanese number is the anchor everything else is built from.
• US and UK sizes are built on the barleycorn — an old English unit of one-third of an inch (about 8.47 mm). One full size up is one barleycorn longer; a half size is roughly 4.2 mm. The two countries just start counting from different points, which is why the numbers are close but never identical.
• EU sizes use the Paris point, two-thirds of a centimetre (about 6.67 mm) per full size. That’s why European sizes climb in bigger jumps and run higher numbers — a US 9 lands around EU 42.

So the conversions aren’t arbitrary lookup tables; they’re arithmetic. The Shoe Size Converter works from foot length in centimetres and reports every system at once, but it helps to see the relationships behind it.

How the systems line up

Starting from a foot length in centimetres, the common men’s relationships are:

• Japan / Mondopoint = foot length in cm, directly.
• US men ≈ foot length in cm − 18.5.
• US women = US men + 1.5. Women’s and men’s scales are offset by a size and a half, which is why unisex sneakers list both.
• UK = US men − 1. A US 9 is a UK 8 in men’s shoes.
• EU climbs in Paris points and works out to roughly three times the foot-cm minus about twenty-one — a US 9 / UK 8 sits near EU 42.
• China uses its own metric scale, roughly (foot cm × 2) − 10.

Two takeaways fall out of this. First, the US-to-UK gap of one full size is the single most common conversion mistake — buy a UK shoe at your US number and it’ll be a size too big. Second, men’s and women’s US numbers are not interchangeable: a women’s US 9 is not a men’s US 9. When a chart doesn’t say which it means, check the foot-length column instead.

Why half a size is a big deal

A half size is only about 4 mm of length, which sounds trivial until you remember that it’s also tied to a width grade and that toe shape varies wildly between lasts. Going up a half size for more length also subtly increases the width and the heel-to-ball position, so the shoe can fit differently in more ways than just “longer.” This is why two shoes labelled the same number can fit completely differently — the number describes length, but fit is length plus width plus the shape of the last.

Measure your feet the right way

A conversion is only as good as the foot length you feed it. Measure carefully:

1. Stand up. Your foot spreads and lengthens under your body weight. Measuring while seated gives a number that’s too small.
2. Measure at the end of the day. Feet swell over the course of a day by a few millimetres — fit them at their largest, not their smallest.
3. Heel to longest toe. Your longest toe isn’t always the big toe. Put your heel against a wall, stand on a sheet of paper, and mark the tip of the longest toe.
4. Measure both feet and use the larger one. Almost everyone has one foot slightly bigger than the other. Size to the larger foot.
5. Add toe room. Leave about 5–10 mm of space ahead of your longest toe for walking and running. If your bare foot measures 25.5 cm, size as if it were around 26 cm.

If your tape measure only reads inches, the conversion to centimetres is just × 2.54 — the Custom Unit Converter handles that cleanly, or the shoe tool accepts inches directly.

Brands don’t agree with the chart — or each other

Even a perfect conversion only gets you to the nominal size. Real shoes are built on lasts that run large or small, and the well-known patterns are worth memorising:

• Nike tends to run about half a size small — many people go up a half.
• Adidas is generally true to size.
• Vans is true to size, though width varies by model.
• Converse famously runs about half a size large — size down.
• New Balance is true to size and one of the better brands for wide options.
• Birkenstock comes in EU sizes only, and its footbeds run roomy — narrow feet should round down.

Treat the converted number as your starting point, then nudge it by the brand’s known tendency. When you can, check the brand’s own size chart in foot-length centimetres rather than trusting that their “9” matches everyone else’s.

A note on accuracy

These conversions are approximate by nature. Sizing systems were never perfectly standardised, half sizes round differently between makers, and width grades (B, D, 2E and so on) aren’t captured by the length number at all. Use a conversion to get into the right range, then rely on foot length in centimetres and the brand’s fit notes to land the exact pair. For hard-to-fit feet, ordering two adjacent sizes and returning one is still the most reliable approach.

Frequently asked questions

What is a US 9 in EU sizes? A men’s US 9 is roughly an EU 42 and a UK 8. The European number is higher because EU sizing counts in smaller Paris-point steps from a different starting point.

Are men’s and women’s sizes the same? No. In US sizing, women’s numbers run about 1.5 sizes higher than men’s for the same foot length, which is why a women’s 10.5 and a men’s 9 are close in actual length.

Why do two shoes in my size fit differently? The number only encodes length. Width, toe shape and the last the shoe is built on all change the fit, so two correctly-sized shoes can feel completely different.

Measure your foot in centimetres, drop the number into the Shoe Size Converter, and you’ll get US, UK, EU, Japanese and Chinese sizes side by side — then adjust for the brand and you’ll order the right pair the first time.