Measure the foot, then use the chart
Every conversion on this page hangs off foot length in centimetres, because that is the only figure in the whole business that means something physical. Everything else is a label.
To measure: stand on a sheet of paper with your heel against a wall, late in the day when your feet are at their largest, wearing the socks you intend to wear with the shoes. Mark the paper at the end of your longest toe -- which is not always the big toe -- and measure from the wall to the mark. Do both feet and use the longer one. A difference of 3 to 5 mm between feet is completely normal and is the reason the smaller foot ends up in a slightly loose shoe rather than the larger one being crushed.
Then add a little. The measurement is your foot; the shoe needs room. Around 1 cm of space in front of the toes is the usual allowance for everyday shoes, and running shoes are often bought a half size up on top of that, because feet swell over distance.
How the systems relate, and where they stop relating
US and UK sizes both come from the barleycorn, an old unit of one third of an inch, which is why one full size is 8.5 mm of length and a half size is about 4 mm. The two scales start counting from different points, which is where the roughly half-size offset between them comes from. EU sizes are built on the Paris point of two thirds of a centimetre, so an EU size is about 6.7 mm -- close to a US half size but not equal to it. That mismatch is why the columns in the chart above drift in and out of alignment rather than stepping neatly, and why some US half sizes end up sharing an EU number.
| System | Step size | What it counts |
|---|---|---|
| US and UK | 8.5 mm per full size, 4.2 mm per half | Barleycorn, one third of an inch |
| EU | 6.7 mm per size, no halves | Paris point, two thirds of a centimetre |
| cm / mondopoint | 5 mm steps typically | Foot length directly |
The centimetre system is the honest one. Japanese sizes, Korean millimetre sizes and the mondopoint scale used for ski boots all label the shoe with the foot length it is meant to fit, which removes an entire layer of guessing.
Men's and women's are the same shoe, numbered differently
US women's sizes run about 1.5 numbers above US men's for the same foot: a women's 8 and a men's 6.5 are close to the same length. This matters when you buy a unisex model such as a skate shoe or a running trainer sold in one size run, and it matters when a sale only has one line left.
Length is not the whole story, though. Women's lasts are generally cut narrower through the heel and slightly higher in the instep, so a foot that measures right in a men's shoe may still slip at the heel, and a wide foot may find the men's version more comfortable at the equivalent length. The UK does not apply the same offset -- UK sizes are nominally the same scale for both -- which is one more reason two charts of the same conversion can disagree.
Why charts disagree, and which one to believe
There is no standards body enforcing any of this. Nike, Adidas, New Balance and Clarks each publish their own conversion, and they do not match. The clearest example is UK sizing for men: some charts put US 10 at UK 9.5, others at UK 9, and both are defensible because the underlying scales were never formally reconciled. This page uses the half-size offset and says so, rather than presenting one convention as the truth.
On top of the chart problem sits the last problem. A last is the form a shoe is built around, and two shoes from the same brand in the same nominal size can differ by a noticeable amount if they use different lasts. Running models frequently run small. Italian dress shoes commonly run narrow and long. Skate shoes run wide.
So the working advice: measure your foot in centimetres, look up the brand's own chart for the specific model, and treat any general conversion table -- this one included -- as a starting point that tells you which two sizes to compare rather than which one to buy.
Buying online without trying them on
- Find the brand's chart for that model line, not the retailer's generic one.
- Check whether the chart lists foot length or shoe length. If a chart says a size is 28 cm and your foot is 28 cm, that shoe is probably too small -- the number usually refers to the foot the shoe is designed for, but not always.
- Read reviews for the phrase "runs small" or "runs large". A consistent pattern across many reviewers is better evidence than any chart.
- Check the return policy before ordering, and order one size only. Ordering two sizes to keep one works for some retailers and is expensive with others.
- Width is a separate axis. US shoes come in D as standard for men and B for women, with 2E and 4E as wide options. Most European brands publish no width at all and just run narrow.
Questions people ask
Is US 10 the same as UK 9 or UK 9.5?
Both answers appear in published charts. The scales were never formally reconciled, so brands made their own choices: some put US men's 10 at UK 9.5, others at UK 9. This page uses the half-size offset. In practice the difference is 4 mm of length, which matters at the edges of a fit and not much in the middle, but it is the reason to check the brand chart before ordering across the Atlantic.
How do I convert a men's size to a women's?
Add about 1.5 to go from US men's to US women's, subtract about 1.5 to go the other way. A men's 8 is roughly a women's 9.5. The length matches; the shape does not necessarily, since women's lasts are usually narrower in the heel and higher in the instep.
My foot measures 27 cm. What size is that?
About a US men's 9 or a US women's 10.5, which is EU 42.5 or so. But that is the bare foot measurement, and a shoe that is exactly your foot length will be too short. Allow around 1 cm in front of the toes, and more for running. Compare against the brand's own chart, which will often list the foot length each size is designed for.
Why does the same size fit differently in two shoes from one brand?
Different lasts. The last is the form the shoe is built on, and a brand uses several -- a running last, a court last, a dress last. Size is only a length label; the width, instep height and toe box shape all change with the last, and none of them appear in a conversion chart.
What about kids' sizes with C and Y?
In US kids' sizing, C is the toddler run and Y is the youth run, and the numbering restarts: 13C is followed by 1Y. A 1Y is a whole size larger than a 13C, not smaller. The youth run tops out around 7Y, which is close to a US men's 7 or a women's 8.5, and buying youth sizes is a well-known way to pay less for a small adult foot.