Shoe Size Conversion: Everything you need to know

Confused by EU, US and UK footwear sizes? Nervous about shopping for shoes online? Let us demystify the shoe size conversion process and help you find the perfect fit... 

Why can shoe size conversion tables be flawed?

The issue for manufacturers and retailers when trying to convert EU sizes to UK or US, is that it’s a bit like comparing centimetres and inches; the scales are misaligned. There are 6.66mm between each European size, and 8.46mm between each UK or US size. 

And the bad news for us longer-footed ladies? Conversion becomes even more inaccurate the bigger your shoe size. When a retailer attempts to align two scales that are completely out-of-whack with one another, it comes as no surprise that by the time they’ve climbed the scale to the larger sizes, the disparity between EU and UK (and hence the room for error) is huge. You only have to compare your different sneaker brands (look at the size conversion label on the tongue), to realise that it’s all over the shop. So while online shoe shopping is usually pretty low-risk for your shorter-footed pals, it can be a bit of a minefield for us. 

Why are the scales different?

Here's the super geeky bit. The European shoe scale is based on “The Paris Point”, a unit of measurement that corresponds to 3.33mm, and was used to define half a shoe size by old French shoemakers in the 1800s. It is commonly used by continental Europe, Russia and former USSR countries. 

The British scale is based on the “Barleycorn” measurement, and is equal to a third of an inch, or 8.47mm. In olde world England, 3 barleycorns served as the measurement for 1 inch.

UK to US size conversion is a little easier; the US industry adopted this barleycorn scale later, but (to make things just that little bit more tricky for us) two sizes out from ours. i.e, a UK size 8 is a US size 10. 

Shoes being made in 1800s


Why does Otto + Ivy use EU sizing instead of UK sizing?

Otto + Ivy is a British brand. But if you’re also from the UK, you’ve possibly noticed that tall British women tend to be acutely more aware of their European shoe size than short British women, who don’t usually need to trouble themselves with such calculations (they’re at the beginning of the sizing scale, before it’s all gone tits-up, after all). I wouldn’t generally buy a size 9 shoe without enquiring as to whether it was a “43” 9 or a rogue “42” 9, for example, but my size 5 friend doesn't give such things a second thought. 

With only 6.66mm between each size, the EU scale is generally much more accurate and consistent across different brands — and since our customers are usually au-fait with their European size, we use this instead. 

Why am I a different size in differing styles?

Most people are the same size across the board in Otto + Ivy. But there are lots of factors that can contribute to shoe size, beyond length. The width around the ball of your feet, the depth from the top of your toes to the floor, your instep, the length of your toes, and whether your first, second, or even third toe are the longest of the bunch will all contribute, and can mean that certain styles will fit you differently. 

If you have a long second/third toe, for example, you may fit a pointed flat in the same size as someone with shorter feet than you. But they may take a smaller size than you in an open-toe sandal. 

This is also why we give the measurement of the shoes — not your feet — on product pages. Sizing isn’t all about length alone, so we ask that you compare the length of the shoes to a similar style that you already own. Or yell for help!

How Otto + Ivy can help

It can be a little bit overwhelming trying to work out what size to buy yourself, particularly if shopping for the first time. But we work really hard to ensure that there is consistency in sizing across Otto + Ivy, and alignment with other brands that use EU sizing. And, if a shoe does seem to be coming up a little small or large based on customer feedback or our experience, we’ll tweak future production runs or offer advice on our product pages. (See the “How do I fit?” section on each individual product page). We’ll NEVER try to make you buy something that we don’t think will work for you… which is why our returns rate is less than half of the average footwear retailer. 

If you need further assistance, particularly if you’re purchasing for the first time, or perhaps from abroad and want to ensure you’re getting the size right, then we’re more than happy to help if you email us with the following information:

  1. A measurement that MUST be carried out as follows. Stand with back of heel to wall and measure from wall to front of toes in a straight line. We’ll need the measurement in mm for accuracy. Remember that accuracy is important as there are only 6.66mm between sizes :) Don’t say “My feet are about 28cm”… it won’t help!)
  2. Which is your longest toe? (Usually first or second).
  3. What style(s) are you looking to buy on Otto + Ivy?
  4. Where have you bought shoes previously and what sizes do you tend to be? 
  5. Write MEASUREMENT FROM WALL in your email subject line, so we know that you’ve measured correctly… this saves us a lot of time back and forth!

You can see our Shoe Size Conversion Chart here, but please remember that — due to differing scales in different countries — this is only to be taken as a loose guide. We always suggest going by your European size if you know it. 

Do I need to size up if it’s a pointed shoe? 

No… we’ve accounted for the point in all of our designs and fitting sessions. 

What about different widths?

We usually ask you to purchase by width based on your experience of shoe shopping, since measuring width at home can be fraught with complication (a lot will depend on depth, foot shape, bunions, toe length…), but we are again more than happy to help via email if you’re really stumped on this. You can email us with a photo of you feet and a measurement around the widest part of your feet (usually just below toes). 

What about half sizes?

Otto + Ivy doesn’t offer half sizes, but if you’re frequently between sizes, you can email us to ask what size we’d suggest in each style. It may be that an insole will help in a shoe that is slightly too wide or long for you. We also offer some tips in the "How do I fit?" section of each product page. 

Shoe Lasts in a size 43

So yes… shoe sizing is a complex game. But good fit is at the core of Otto + Ivy, and we spend a LOT of time ensuring that your experience of shopping with us is as seamless as possible. We’re constantly listening to feedback, making tweaks if necessary, and keeping returns low.

So head to our shop and find your perfect fit with confidence. Any other questions, drop us an email or message us on Instagram.

Laura xx

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