US vs UK vs EU Shoe Sizes Explained: Why Your Size Changes at the Border
How US, UK, EU and cm shoe sizing systems actually work, why they never line up cleanly, and the exact offsets to use when you buy shoes abroad.
If you have ever ordered a “US 9” from a UK retailer and received something that fit like a 10, you have run into the fact that there is no single shoe size. There are at least four systems in daily use, each with a different starting point and a different step size, and retailers translate between them with varying levels of care. Once you understand the underlying math, the errors become predictable and easy to avoid.
The four systems, in one table
| System | Unit of one full size | Where “size 0” starts | Used by |
|---|---|---|---|
| US | 1/3 inch (8.47 mm) | ~3 11/12 inches (men), ~3 7/12 inches (women) | USA, Canada |
| UK | 1/3 inch (8.47 mm) | 4 inches (12 barleycorns) | UK, Ireland, India, South Africa |
| EU (Paris point) | 2/3 cm (6.67 mm) | 0 cm | Continental Europe, most of LatAm |
| Mondopoint (cm/mm) | 1 mm or 5 mm | Actual foot length | Japan, Korea, China, ski boots, military |
Two things to notice. US and UK share the same step (a third of an inch) but start at different points, which is why they are a fixed offset apart. EU uses a smaller step, which is why it drifts against US and UK across the range. And only the cm/mm system describes the foot directly; the others describe the last, the wooden or plastic form the shoe is built around.
US to UK: subtract one (men) or two (women)
For men’s shoes the rule is simple: UK = US − 1. A US 9 is a UK 8. Retailers such as Clarks and Dr. Martens, which build on UK lasts, print both numbers and they always sit exactly one apart.
Women’s shoes are messier. The traditional US women’s scale is offset from the men’s scale by 1.5 sizes (a US women’s 10.5 sits on the same last as a US men’s 9). Combine that with the UK offset and UK women’s ≈ US women’s − 2, though some brands use −2.5. This is the single most common women’s conversion error I see: buyers subtract one, as they would for men, and receive a shoe a full size too big.
Use the women’s shoe converter rather than doing this in your head. The men’s equivalent is at men’s shoe sizes.
US to EU: the drift problem
Because an EU size is 6.67 mm and a US size is 8.47 mm, four EU sizes are roughly worth three US sizes. There is no constant offset. Near a US 7 the difference is about 33; near a US 12 it has grown to 34 or 35. That is why conversion charts show EU 42 as “US 8.5” on one site and “US 9” on another. Both are defensible roundings.
The reliable approach is to convert through millimeters. A US men’s 9 is intended for a foot of roughly 270 mm. On the Paris point scale, a 270 mm foot plus about 15 mm of toe allowance gives a 285 mm last, and 285 / 6.67 = 42.7, so EU 42.5 or 43 depending on the brand’s rounding policy. Adidas rounds this way; Nike lists EU 42.5 for US 9; Salomon and Ecco list EU 43.
Which brands use which base
Knowing what a brand’s “home” system is tells you which number on the label to trust.
- Nike, Adidas, New Balance, Converse: US base. The US number is authoritative; EU and UK are derived. See Nike sizing, Adidas sizing and New Balance sizing for the brand-specific drifts.
- Clarks, Dr. Martens, Church’s, Loake: UK base. Trust the UK number.
- Birkenstock, Ecco, Geox, Camper, Veja: EU base. Trust the EU number, and note Birkenstock has no half sizes at all.
- Asics, Mizuno, Onitsuka Tiger: Japan base, so the cm figure on the box is exact. Their US conversion is fairly generous; many people go down half a US size in Asics compared to Nike.
Half sizes and the missing sizes
US and UK offer half sizes across the whole adult range. Many EU-based brands do not: Birkenstock, Crocs and most Italian dress shoe makers sell whole EU sizes only, which puts you between two sizes around a third of the time. Since a full EU step is only 6.67 mm, being between sizes is less painful than in the US system, but the general rule still holds: size up and use an insole if needed.
Kids’ sizing has its own trap. US children’s sizes run 0–13, then restart at 1 for youth. A “size 1” can therefore be an infant shoe of about 85 mm or a youth shoe of about 205 mm. The UK system has the same restart. EU and cm keep counting upward without a break, which is one reason the kids’ shoe size converter works from foot length rather than from a label.
Practical rules for buying across systems
- Measure your foot in millimeters and convert from that, never from another shoe’s label. The method is in how to measure your foot at home.
- Find the brand’s base system and read that number on the product page. Ignore the derived numbers if they conflict.
- For EU conversions, expect rounding. If the site’s chart puts you at 42.5 and the shoe only comes in 42 and 43, go to 43 for anything you will walk in for hours.
- For women’s US to UK, subtract two, not one.
- Japanese and Korean brands are cm exact. Match your foot length directly and skip the conversion.
FAQ
Is a UK 8 the same as a US 8?
No. In men’s shoes a UK 8 is a US 9. In women’s shoes a UK 8 is roughly a US 10. The UK scale starts a full size later than the US scale because it counts from a four-inch last, while the US men’s scale starts a third of an inch earlier.
Why does the same EU size show different US sizes on different websites?
EU sizes are 6.67 mm apart and US sizes are 8.47 mm apart, so they never line up exactly. Each brand rounds the mismatch in its own direction. Nike and Adidas each publish their own EU-to-US table, and they disagree by half a size at several points.
Which system is most accurate for buying online?
Centimeters or millimeters. It is the only system that measures the foot rather than the shoe form. When a product page lists a cm figure, compare it directly with your measured foot length and add 10–15 mm for toe room; that beats any letter-and-number conversion.