Converting sneaker sizes: EU, US, UK and measuring properly

Shoe sizes evolved historically and are based on different units of measurement. Continental Europe uses the Paris point: one size equals two-thirds of a centimetre, or roughly 6.7 millimetres. The UK counts in "barleycorns", a third of an inch (about 8.5 millimetres). The US uses its own system derived from the British one, with a different starting point – and separate scales for women and men.

Importantly, all three systems actually refer to the length of the last – the form the shoe is built over – not to your foot. The last is longer than the foot because the shoe needs some allowance. How large that allowance is, each manufacturer decides for itself. That's why EU 42 can fit differently at Nike than EU 42 at adidas or Puma.

The most reliable basis for any online purchase is your foot length in centimetres. Many brands state it directly on the label or in the size chart (usually as "CM" or "JP"). Here's how to do it:

As a rule of thumb for men's sizes, the US size is half to a full size above the UK size, depending on the brand. In the US system, women's sizes are shifted by 1 to 1.5 sizes compared with men's – so at Nike a US women's 8 corresponds to roughly a US men's 6.5. For unisex models, the EU size is the same for both sexes.

For orientation, here are some reference values from Nike's men's size chart (foot length → US → EU). Brand charts are adjusted from time to time, so check the current chart for the specific model before buying:

adidas consistently gives EU sizes in thirds: 42, 42 2/3, 43 1/3, 44 and so on. This isn't a marketing gimmick but the exact conversion of UK half sizes into Paris points. At adidas, UK 8 corresponds to EU 42, UK 8.5 to 42 2/3 and UK 9 to 43 1/3. Puma and some other brands also sometimes give only UK sizes on their labels.

For you, this means: if you wear EU 42.5 at Nike, 42 2/3 will usually fit at adidas – but not always. The safest approach is still to check the foot length in the brand's chart. Bear in mind, too, that individual models from the same brand vary: a narrow adidas Samba fits differently in the same size than a roomy running shoe.

Between the tip of your longest toe and the end of the shoe there should be about 0.5 to 1 centimetre of space in everyday sneakers, and around 1 centimetre in running shoes – roughly a thumb's width. When walking, and especially when running, the foot slides forward and expands. Shoes that are too tight lead to black toenails and blisters; shoes that are too big cause rubbing at the heel.

Length is only half the story, though. Width and instep height are just as important. If a sneaker pinches at the sides in the right length, a bigger size is often the wrong solution – you'll then slide forward into it. Better: a model with a wider last or a width variant. New Balance and ASICS offer many models in widths such as "2E" (wide) or "4E" (extra wide).

The following are experience-based values that come up again and again in retailers' sizing advice and among many wearers. They don't replace trying shoes on, but they help with a first assessment:

In Germany, you have a 14-day right of withdrawal when buying from commercial online retailers. Many shops voluntarily offer longer return periods. This makes it easier to order two sizes and send back the one that doesn't fit. Just make sure you only try the shoes on indoors and on a clean floor so they're accepted back as new. Private sellers on marketplaces usually don't offer a right of withdrawal – there, you should be particularly sure about the size.

One last tip: make a note of which size fits you for each brand and model. If you already own a sneaker that fits perfectly, its label is the best reference for your next purchase – especially if it also shows the size in centimetres.

Children's shoes come with additional abbreviations. In the US, kids' sizes run on a separate scale, marked "C" (Child) or "K" (Kids), followed by youth sizes marked "Y" (Youth). Nike and Jordan also use the abbreviations TD (Toddler), PS (Preschool) and GS (Grade School). GS sizes go up to around EU 40 and are therefore also interesting for adults with small feet – they're often cheaper, but sometimes differ from the adult model in materials and details.

Children need a larger allowance than adults: around 12 to 17 millimetres in front of the longest toe makes sense, leaving room to roll through and a little growing room. Measure children's feet regularly, because children rarely notice when a shoe has become too small.

Many sneakers come in women's and men's versions with slightly different colours. In principle you can wear either, as long as you convert correctly. The EU size stays the same, while the US size usually shifts by 1.5 (by 1 at adidas). Women's models are often cut slightly narrower; men with slim feet usually get on well with them, while women with wide feet often benefit from men's or unisex models. When looking at offers, check whether the size is given as "W", "WMNS" or "M" – otherwise you can easily end up ordering one and a half sizes off.

Brand size charts are the most reliable basis because they refer to foot length. Comments such as "runs small" in product reviews or shops' size advisers are a useful addition, especially for models with an unusual cut. But don't take them as gospel: whether a shoe feels "small" also depends on foot shape, socks and personal preference. If several independent sources say the same thing, you can rely on it more.