Shoe Size Converter: Korea (mm), US, EU, UK, Japan
Only the Korean and Japanese systems state an actual length. A Korean 250 means a foot 250mm long; every other country's number is a convention. That is why a reliable conversion always travels through millimetres.
Shoe sizing mixes two different kinds of number. Korea's 250 and Japan's 25 are measurements — the Mondopoint system writes down the length of the foot itself. A US 7, an EU 40 or a UK 6.5 is closer to a position in a sequence than a dimension.
The distinction matters because it tells you where error enters. A millimetre figure is something you measured and cannot really be wrong about. The moment you translate it into a US or EU number, brands start disagreeing with each other. Work from the certain end towards the uncertain one.
Korean sizes are a measurement, not a conversion
Korean sizes are millimetres and Japanese sizes are centimetres. They are the same quantity written in different units, so a Korean 250 is always a Japanese 25 and no lookup table sits between them. In this tool the two columns are derived from each other rather than typed in separately.
This makes the most accurate way to use the converter obvious: measure your foot and enter the length. Stand with your heel against a wall and measure to the tip of the longest toe — check which toe that actually is, because it is not always the big one.
When you measure changes the answer too. Feet swell over the course of a day, so an evening measurement runs larger. That is why a shoe bought on a morning fitting can feel tight by the afternoon.
The size does not include room to move
A foot that measures exactly 250mm does not necessarily take a 250. The foot needs space to slide forward inside the shoe, and it lengthens slightly under load as you walk.
For trainers the usual allowance is 5–10mm, so a 255mm foot often wears a 260 or 265. Dress shoes take less; running shoes usually take more. If your foot is wide or high in the instep, length alone will not settle it and you need the width marking — 2E, 4E and so on — as well.
This tool deliberately does not add an allowance. It reports the size matching the length you entered, because how much room to leave depends on the kind of shoe, and baking in a number would get in the way more often than it would help.
Men's reference
The Korean and Japanese columns are the foot length itself; the rest are the conventional numbers for that length.
| Korea (mm) | Japan (cm) | US | UK | EU |
|---|---|---|---|---|
| 250 | 25 | 7 | 6.5 | 40 |
| 260 | 26 | 8 | 7.5 | 41 |
| 270 | 27 | 9 | 8.5 | 42.5 |
| 280 | 28 | 10 | 9.5 | 44 |
| 290 | 29 | 11 | 10.5 | 45 |
US women's sizes are where charts disagree
US men's and women's sizes give different numbers to the same foot, and the gap between them is not fixed. This tool's chart uses a one-size difference. Plenty of brands use one and a half, and some — Converse most famously — use two.
So when buying women's shoes from a US site, do not carry the US number across. Find the cm or mm column in that brand's own size chart instead; nearly every brand publishes the measured length alongside its sizes, and that column is the one that means the same thing everywhere.
The US-to-UK relationship is better behaved: US men's runs 0.5 above UK, and US women's runs 2 above.
Measuring properly
- •Put a sheet of paper on the floor against a wall and stand on it.
- •Measure standing, with your weight on the foot. Measuring seated gives a shorter reading.
- •Mark the tip of the longest toe and measure back to the wall in millimetres.
- •Measure both feet and size to the larger one. A difference between them is normal.
- •Measure in the evening, when your feet are at their largest.
- •Wear the socks you intend to wear with the shoes — thick socks can account for nearly 5mm.
Extended FAQ
Are Korean and Japanese shoe sizes different?
Only in the unit. Korea writes the length in millimetres as 250, Japan writes the same length in centimetres as 25. There is nothing to convert.
My foot is 255mm — do I buy a 255?
Usually not. Shoes need room inside, and for trainers people typically go 5–10mm above their measured length. This tool reports the size that matches your measurement without adding an allowance, so add it yourself according to the type of shoe.
How do I convert to US women's sizes?
Use the brand's own chart. The offset from men's sizing varies between one and two full sizes depending on the maker. Almost every brand lists cm alongside its sizes — match on that number instead.
Why do children's sizes count back down?
US and UK children's sizing runs up to 13 for little kids and then restarts at 1 for youth sizes. The same number means two very different shoes depending on which band it belongs to, which is another reason to confirm children's shoes in millimetres.
Is anything I enter stored?
No. The conversion runs in your browser and nothing is sent to a server.