The Complete Guide to International Shoe Sizes: US, UK, EU, Mondopoint, JP and Kids' Sizing
Few things are more frustrating than ordering shoes from another country and discovering they don't fit. A US men's 9 is not a UK 9, a European 42 means different things on different lasts, and Japanese sizes look like they belong on a ruler rather than a shoebox. This guide explains every major shoe sizing system in the world, how they relate to each other, and how to measure your feet so you can buy footwear from anywhere with confidence.
Why shoe sizes are such a mess
Shoe sizing grew up locally, long before global e-commerce existed. Cobblers in London, Paris and Boston each invented their own numbering, based on their own units and their own ideas of what a "size step" should be. The American system grew out of the English barleycorn — one third of an inch per full size. The European system grew out of the Paris point, two-thirds of a centimetre per size. The Japanese, arriving later, skipped the historical baggage entirely and simply stamped the foot length in centimetres on the box. The result is a patchwork: the same physical foot can legitimately be labelled US 9, UK 8, EU 42 and JP 27, depending on where the shoe was made. There is no single worldwide standard for fashion footwear, which is exactly why conversion tools like the one above exist.
US sizing: men's, women's and the 1.5 rule
American sizes step by one-third of an inch (about 8.46 mm) per full size, with half sizes splitting the difference. The catch that trips up most shoppers is that men's and women's US sizes are not the same scale. A US women's size is roughly 1.5 sizes larger in number than the equivalent men's size: a US men's 8.5 and a US women's 10 fit essentially the same foot. Unisex sneakers are usually labelled in men's sizes, so women buying unisex shoes should go down 1.5 sizes — a woman who wears US 8 should pick US 6.5 in a men's-labelled shoe. US sizes also run from very small (youth and children's ranges) up past 16 for men, and the scale is continuous: children's size 13C flows directly into youth size 1Y, a detail that confuses many parents but is simply one numbering restarting.
UK sizing: close to US, but one off
The British system shares the barleycorn step with the American system but starts counting from a different zero point. In practice, a UK men's size is about one full size smaller in number than the US men's equivalent: US men's 10 is UK 9, and the same one-size offset holds across most of the adult range. Women's UK sizes follow the same relationship relative to women's US sizes. Children's UK sizes also exist on their own continuous scale, which is why a UK kids' 13.5 sits right next to a UK kids' 1. Because the UK and US scales look so similar on paper, shoppers constantly mix them up — always check which country's scale the label refers to before assuming your usual number.
EU sizing and the Paris point
Continental European sizes are based on the Paris point, equal to two-thirds of a centimetre (6.67 mm). The same scale serves men and women, which is convenient, but the system has a quirk: because 6.67 mm steps don't line up neatly with the 8.46 mm steps of the US and UK systems, brands round to the nearest convenient EU number. That is why you will see the same foot labelled EU 42 by one brand and EU 42.5 by another — neither is wrong, they simply rounded differently from the underlying foot length. EU sizes also tend to run in half steps (39.5, 40.5) in the middle of the range, and some brands skip certain halves entirely. If you are between two EU sizes, the brand's own centimetre chart is more trustworthy than the EU number alone.
Mondopoint: the honest system
Mondopoint is the international standard defined by ISO/TS 19407:2015, and it is refreshingly literal: the size is simply your foot length in millimetres. A 270 mm foot takes Mondopoint 270. No barleycorns, no Paris points, no gender offsets — Mondopoint does not differentiate between men and women at all. It is the standard for ski boots, military footwear and much of Asia. Japan uses the same idea expressed in centimetres, so JP 27 and Mondopoint 270 describe the same foot. When a converter or a brand gives you a Mondopoint number, you are looking at the most objective measurement in the shoe world. If every brand printed Mondopoint on the box, size conversion charts would be unnecessary — which tells you everything about why the legacy systems persist.
Kids' and baby sizes: C, Y and the great restart
Children's sizing is where even experienced shoppers get lost. In the US system, children's sizes carry a letter: C for child (toddlers and little kids, roughly 1C to 13C) and Y for youth (big kids, 1Y to 7Y). The numbering restarts at the handoff — 13C is immediately followed by 1Y, and they are consecutive sizes on one continuous scale, not a dramatic jump. UK kids' sizes have their own version of the same restart (12.5 to 13.5 to 1), and EU kids' sizes simply continue upward without letters, which is arguably the clearest of the three. Baby sizes start around US 1C (about 7 cm of foot) and the letters matter enormously: a toddler's 4C and a youth 4Y are wildly different shoes. Because children's feet grow fast — sometimes a full size in a single season — experts recommend leaving 0.4 to 0.5 inches (1 to 1.2 cm) of growing room and re-measuring every two to three months.
How to measure your feet at home
You don't need any special equipment. Tape a blank sheet of paper to a hard floor against a wall, stand on it with your heel touching the wall, and mark the tip of your longest toe — note that this is not always the big toe. Measure from the wall edge of the paper to the mark in centimetres or millimetres. Do both feet and keep the larger number. Measure in the evening, wearing the socks you intend to use, because feet swell during the day and can measure up to half a size larger than in the morning. Compare your measurement to a Mondopoint column first — it is the most direct translation of what you just measured — and round up to the nearest 5 mm step if you fall between steps. The printable ruler on this page is drawn at true scale for exactly this job; just remember to print it at 100 percent, not "fit to page".
Fit rules the charts can't give you
A conversion chart gets you the right number, but fit is about more than length. Leave a thumb's width — about 1.2 cm — between your longest toe and the front of the shoe; toes should never touch the end when you stand. If you fall between two sizes, size up for running and athletic shoes, since feet expand with heat and impact, and consider sizing down for snug dress shoes or heels that will stretch slightly. Width is the dimension most shoppers ignore: standard medium width is D in men's and B in women's, and a shoe that is long enough but too narrow will always feel "too small". Look for W, 2E or 4E fittings instead of simply going longer. Finally, remember that different shoe types fit differently by design — a trail runner, a leather oxford and a ski boot in your "same size" will feel like three different sizes, and that is normal.
Buying shoes internationally online
Cross-border shoe shopping is where conversions earn their keep. Japanese marketplaces list JP or centimetre sizes almost exclusively; European boutiques list EU; American retailers list US. Start from your measured foot length in centimetres, find the Mondopoint or JP equivalent, and then read the specific brand's own size chart — reputable brands publish the foot length each size is built for, and that column overrides every conversion. Be honest with yourself about variance: the same nominal size can differ by several millimetres between brands because lasts (the foot-shaped forms shoes are built on) differ. Check return policies before ordering across borders, since return shipping can cost more than the discount you were chasing. And when a product page shows multiple systems on one label — "US 9 / UK 8 / EU 42 / 27 cm" — trust the centimetre figure most.
How to use the StrideScale converter
Pick the system you already know from the dropdown — US men's, US women's, US kids, UK, EU or Mondopoint/JP — type the size, and the tool shows every equivalent instantly, flagging it when your input falls between standard rows so you know it's the nearest match rather than an exact one. If you don't know your size in any system, use the foot-measuring wizard: enter your measured foot length and get recommended sizes everywhere, plus a printable ruler and tailored fit notes. Parents can jump to the kids' tab for C and Y conversions or browse the full baby, toddler and youth charts below. Everything runs in your browser, conversions are unlimited, and nothing is uploaded anywhere.