Figuring out shoe sizes can sometimes feel like trying to solve a tricky puzzle. If you’ve ever tried converting your shoe size between US, EU, and UK systems, you might have noticed something frustrating — the sizes don’t line up perfectly. That’s because these sizing systems aren’t exact translations of each other but more like rough guidelines, each with its own quirks.
Why Are There Different Sizing Systems Anyway?
The US, UK, and EU sizing systems all developed separately over time, reflecting different measurement preferences and history in each region. So, it’s no surprise they don’t sync up perfectly. For example, the US and UK systems are pretty similar but differ in where size 1 starts and how they treat men’s and women’s sizes. The increments between sizes come from an old measurement called a “barleycorn” (about ⅓ of an inch — yes, from an actual barley kernel!).
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US vs UK: Men’s US size is usually one size bigger than UK (so US 9 is roughly UK 8), and women’s US sizes are generally 1.5 to 2 sizes bigger than UK.
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EU system: Uses centimeters, with each size increasing by 0.75 cm. Sounds simple, right? Well, not quite — converting between EU and US sizes can be confusing because they’re based on different metrics.
Why Don’t Sizes Match Exactly?
Here’s a fun example: An EU 42 shoe roughly equals a US 10.5, which is easy enough. But EU 39 translates to about US 8.2 — and you’ll never see a US 8.2 marked on shoes. Instead, brands just call it US 8, which can feel a little big if you expect a perfect US 8 fit.
It Gets More Complicated With Brands
Different brands follow different sizing rules. Some use US sizing as their base (like Altra or Xero Shoes), while others use EU sizing (like Freet or Vivobarefoot). So an EU 42 in one brand might feel like a US 9, but in another, it might fit closer to a US 8.5. Plus, brands sometimes tweak their sizing internally, meaning the same “size 9” can feel different between brands — especially with barefoot or minimalist shoes where fit and foot movement take priority.
More Than Just Length: Width, Depth, and Shape Matter Too
Sizing isn’t only about length. Width is often overlooked but can make a huge difference. A size 9 can come in narrow, regular, wide, or extra-wide, depending on the brand. If you have wide feet, a regular width shoe might feel tight, especially in the toe box — and some brands like Altra offer wider toe boxes to let your toes spread naturally.
Depth or volume — the space inside the shoe above your foot — is another factor. People with high arches or “higher-volume” feet need more depth. Too much depth, though, can feel sloppy for people with flatter feet.
Toe box shape and heel fit also matter. Barefoot shoes usually have wider toe boxes, while traditional running shoes taper. Heel cups vary, too — some fit snug, others are roomy — so knowing your foot shape helps.
Using Centimeters: The “Metric” Advantage?
Some brands list shoe length in centimeters, which can feel more precise than numbered sizes. But watch out — not all brands measure the same way or leave the same “toe room” allowance. Also, your foot length can change during the day due to swelling, so a perfect fit in the morning might feel tight later on.
The Best Way to Find the Right Fit? Try Them On!
With all these variables — length, width, depth, shape, and brand differences — the only real way to know if a shoe fits is to try it on. Walk, jog, and move in them as you would when using the shoes. Lace them up properly, adjust the fit, and see how they feel all around your foot.
If needed, you can even swap insoles to adjust volume — thinner insoles for more room, thicker ones to fill up extra space.
The Bottom Line
Shoe sizing is definitely not straightforward! Different sizing systems and brand quirks mean you can’t just trust a number. Pay attention to how a brand measures, consider width and shape, and don’t be afraid to try on multiple sizes and brands. Ultimately, the shoe that feels right is the best shoe for you — not necessarily the one with the “correct” number on the label.
Happy shoe hunting! 👟✨
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