What's the best way to filter shoe sizes across multiple standards?

Question

Say you have a shoe store and you sell shoes across many different brands. Each brand has its own country of origin, and thus its own sizing standard. We have shoe brands with US sizing, other brands with UK sizes, other brands with IT sizes, and so forth.

What would be the best acceptable way to prompt a user on a product collection screen to filter by size? All customers are in the US, and it's assumed most customers wouldn't know their non-US standard shoe sizing.

Do we present multiple filter areas, each one containing its own standard and set of sizes (eg: "Filter by US Size" box, "Filter by UK size box", etc)? I see a potential challenge here with consumers not knowing what their foreign standard sizing would be.

Or do we combine filters to just "Filter by size" and display sizes in a combined format (eg: "US 3, US 3.5, ..., US 12, UK 3, UK 3.5, UK 4, ..., UK 12, IT 36, IT 36.5, ..., IT 49, etc)? I see the problem here similar to the above, but also users completely missing the fact that there are other sizing standards going on.

Or is there another solution?

Also, with a proposed solution, what is the best way to ensure engagement and visibility across shoes of a similar size but in a different sizing standard?

One line of thought would be in example A above, we create a mapping between standards so that when an option is chosen in one filter box, the related sizes are automatically selected in other sizing standard filters.

This one is really throwing us for a loop as to the best way to present and handle this crucial interactive component. We are also up against similar challenges in other departments, such as clothing and so forth.

Answer 1

For US customers the filter ought to be only US sizes.

And when filtering, automatically select foreign standard sizes that are compatible with the selected US sizes in the search results.

But when displaying the results, when applicable, show both the US and the foreign standard size for each item in the list.

If the first item in the results is a UK shoe include the UK size but show the US size also.

If the second item is a US shoe just show the US size.

It's important customers know, when they purchase a foreign made shoe, it is made to a foreign shoe size...no surprises when they first examine the shoes. But they always needs reassurance it fits and this can only be accomplished providing the comparable US size. For those two reasons, put the US size first (assurance), in parenthesis (translation), and followed by the country of origin shoe size standard, i.e., the size marked in the shoe.

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