Paris points against barleycorns
European shoe sizes step in Paris points, two thirds of a centimetre. British and American sizes step in barleycorns, a third of an inch, which is about 0.85 cm. Two grids with different spacing laid over the same feet: they meet occasionally and disagree everywhere else, and every awkward thing about international shoe sizing comes out of that.
Two units that do not divide into each other
A Paris point is two thirds of a centimetre, about 6.67 mm. A barleycorn is a third of an inch, about 8.47 mm. Neither is a multiple of the other, and neither is a round number in the other's units. If you lay both scales along a ruler starting from the same point, they immediately drift apart and never fully realign.
That drift is why a conversion chart is a table of nearest matches rather than a formula. It is also why the same foot can be a comfortable EU 42 and an awkward between-sizes UK 8, without anybody having made a mistake.
What one size actually buys you, row by row
Charts print sizes. What decides whether going up will help is the interval between them, and on this chart that interval is not constant: it ranges from 0.4 cm to 0.9 cm, averaging 0.46 cm. The table below gives it for every row.
| EU step | UK step | Foot length gained (cm) | In millimetres |
|---|---|---|---|
| EU 35.5 to 36 | UK 3 to 3.5 | 0.4 | 4 |
| EU 36 to 37 | UK 3.5 to 4 | 0.4 | 4 |
| EU 37 to 37.5 | UK 4 to 4.5 | 0.4 | 4 |
| EU 37.5 to 38 | UK 4.5 to 5 | 0.4 | 4 |
| EU 38 to 38.5 | UK 5 to 5.5 | 0.4 | 4 |
| EU 38.5 to 39 | UK 5.5 to 6 | 0.4 | 4 |
| EU 39 to 40 | UK 6 to 6.5 | 0.5 | 5 |
| EU 40 to 40.5 | UK 6.5 to 7 | 0.4 | 4 |
| EU 40.5 to 41 | UK 7 to 7.5 | 0.4 | 4 |
| EU 41 to 42 | UK 7.5 to 8 | 0.4 | 4 |
| EU 42 to 42.5 | UK 8 to 8.5 | 0.5 | 5 |
| EU 42.5 to 43 | UK 8.5 to 9 | 0.4 | 4 |
| EU 43 to 44 | UK 9 to 9.5 | 0.4 | 4 |
| EU 44 to 44.5 | UK 9.5 to 10 | 0.4 | 4 |
| EU 44.5 to 45 | UK 10 to 10.5 | 0.4 | 4 |
| EU 45 to 45.5 | UK 10.5 to 11 | 0.5 | 5 |
| EU 45.5 to 46 | UK 11 to 11.5 | 0.4 | 4 |
| EU 46 to 47 | UK 11.5 to 12 | 0.4 | 4 |
| EU 47 to 47.5 | UK 12 to 12.5 | 0.4 | 4 |
| EU 47.5 to 48.5 | UK 12.5 to 13.5 | 0.8 | 8 |
| EU 48.5 to 49.5 | UK 13.5 to 14.5 | 0.9 | 9 |
Read the third column and the practical consequence is immediate. Where the step is 0.4 cm, going up a size is a small correction and the shoe above will feel close to the one below. Where it is 0.9cm, the same move is nearly a quarter more room than that. "Just size up" is advice that means different things in different parts of this table.
The offset nobody agrees on
There is one genuine disagreement between published sources, and it is worth naming rather than papering over. Some charts put the US men's number half a size above the UK number, others put it a full size above. This site uses the half-size offset. Both conventions are in use, both are defended, and the difference is never more than half a size.
What both agree on is the foot length. That makes the resolution simple: when a retailer's chart contradicts this one, compare centimetres and you are right either way. This is the whole argument for keeping a measurement column in a chart that could get away with labels alone.
Where the centimetre figure comes from
The centimetre number on a shoe is normally the foot length the shoe is built to fit, not the internal length of the shoe, which is longer. A shoe needs room in front of the toes, usually half a centimetre to a centimetre. If a brand publishes an insole length instead, expect it to read above the foot length in any chart, including this one, and compare like with like before deciding the chart is wrong.
Measure the longer foot, standing, in the afternoon, with the heel against a wall. Both feet are rarely identical and feet lengthen through the day, which accounts for more sizing disputes than any conversion table does. Full instructions are on how to measure shoe size.
For the complete conversion table see the shoe size chart, for a specific size see for example EU 42 to US, and for how the rounding is done see the methodology.
Common questions
Why is there no exact EU equivalent for some UK sizes?
Because the two scales step by different amounts. A UK size is a third of an inch, about 0.85 cm. An EU size is a Paris point, two thirds of a centimetre. Those intervals do not divide into each other, so most conversions land between two rows and get rounded to the nearer one.
Is a half size always the same amount of room?
No, and this is the most useful thing to know about shoe charts. In the EU scale the printed half sizes do not divide the interval evenly, so on this chart the step between neighbouring sizes varies. Going up half a size buys different amounts of length in different parts of the range.
Why do US men's and women's sizes differ by 1.5?
Historical convention rather than anatomy. Both scales are barleycorn scales, a third of an inch per size, but the women's scale starts counting from a different point. The same physical shoe length is a US men's 8 and a US women's 9.5.
Which number should I trust on the box?
The centimetre figure, if there is one. It is the only label that is a measurement rather than a convention, and it is the one that stays true when two published charts disagree about the UK to US offset.
Last reviewed and updated on August 5, 2026. Conversion tables are checked against published international sizing standards.