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How shoe sizes are built: barleycorns, Paris points and centimetres

Updated . 6 minute read.

The short answer

Shoe sizes are lengths in disguise. UK and US sizes count barleycorns (a third of an inch), EU sizes count Paris points (two thirds of a centimetre), and JP or Mondopoint sizes are simply the foot length.

Because a barleycorn is 8.5 mm and a Paris point is 6.7 mm, the scales never line up, and every brand rounds in its own way. Across the 25 brand charts we checked, the formula gives a lower EU number than the brands' median on 15 of 15 US women's sizes.

Four systems, three units

Every system measures the same thing, the length of the last the shoe is built on or of the foot it is built for, and then hides it behind a number.

How each size number is defined. The last is the form a shoe is built around; it is longer than the foot.
SystemUnitHow the number is made
UKBarleycorn, one third of an inch (8.5 mm)3 x last length in inches, minus 25
US men'sBarleycorn3 x last length in inches, minus 24
US women'sBarleycornMen's size plus 1.5 on the common scale, plus 1 on the FIA scale
EUParis point, two thirds of a centimetre (6.7 mm)1.5 x last length in centimetres
Mondopoint, JP, KRMillimetre or centimetreThe foot length the shoe is made for (ISO 9407)
As stated in Wikipedia's Shoe size article. Children's sizes use the same units with a different zero point and are not covered here.

Two things follow. A full US size is 8.5 mm and a half size 4.2 mm, while one EU size is 6.7 mm, so three EU sizes cover a little less than two and a half US sizes. And a US women's size has two definitions: most brands put it 1.5 above the men's size, the FIA scale puts it 1 above. The brand by brand numbers are in men's to women's shoe sizes.

The formula against the brands

Put the definitions together and a US women's size n has a last of (n + 22.5) / 3 inches, which makes the EU size 1.27 x (n + 22.5). The table sets that arithmetic, rounded to the nearest half, beside what brands actually print.

US women's to EU. The formula column is arithmetic; the other columns are read from 25 brand charts checked by hand.
US women'sEU by formulaMost brands printLowest and highest in print
53535 (7 of 20)34.5 to 36
5.535.536 (9 of 21)35 to 36.67
63637 (9 of 25)36 to 37.33
6.53737.5 (11 of 24)36.5 to 38
737.538 (11 of 25)37 to 38.67
7.53838 (8 of 24)37.5 to 39.33
838.539 (9 of 25)38 to 40
8.539.540 (10 of 22)38.5 to 40.67
94040.5 (10 of 25)39 to 41.33
9.540.541 (9 of 23)39.5 to 42
1041.542 (10 of 25)40 to 42.67
10.54242.5 (11 of 23)40.5 to 43.33
1142.543 (9 of 25)41 to 44
11.54344 (8 of 18)42.5 to 44.67
124444.5 (7 of 19)42 to 45.33
Tinted rows: the formula differs from the brands' most common answer. A brand is counted once per answer.

The widest split is at US women's 12, where charts print anything from EU 42 to EU 45 1/3. Which brand prints which number is in US to EU shoe size by brand.

Why brands stray from the formula

  • Rounding. The arithmetic lands between EU sizes most of the time. Some brands round up, some down, and adidas keeps thirds (38 2/3) instead of rounding at all.
  • Toe allowance. The formulas run on last length, and the gap between last and foot is a design choice that changes by brand and by model.
  • Two women's scales. A brand on the plus 1 scale and a brand on the plus 1.5 scale can print different US women's numbers for the same last.

Centimetres are the closest thing to a common language

A Mondopoint or JP size names the foot, not the last, so it skips the toe allowance question. When a brand prints a foot length or a JP size beside its US size, that is the number to compare across brands. It is still the brand's own claim: two brands measure a foot differently, and our converter lowers its confidence when two charts' foot lengths put you more than a size away from the same label.

What to do

  1. Measure the longer foot in centimetres, standing, in the evening.
  2. Find the brand's own chart and look for a foot length or a JP / CM column first.
  3. If the chart has no length, convert with that brand's printed US, UK and EU columns, never with a generic table.
  4. Use the formula only as a sanity check: a brand more than one EU size away from it is telling you its sizing is unusual.
  5. Check the shoe size converter for the brand pair you are moving between.

Common questions

Why is there no exact US to EU shoe size conversion?

US and UK sizes step by a barleycorn, one third of an inch or 8.5 mm. EU sizes step by a Paris point, two thirds of a centimetre or 6.7 mm. The two ladders have different rung spacing, so a US size almost never lands exactly on an EU size and every chart has to round.

What is a Paris point?

The unit of the Continental European shoe size: two thirds of a centimetre. An EU size is one and a half times the length of the last in centimetres, so EU 39 is a last 26 cm long.

Is a CM or JP shoe size the same as my foot length?

That is the idea: Mondopoint and Japanese sizes name the foot the shoe is made for, not the last. In practice some brands print a centimetre size and a separate foot length that differ, so check which one the brand's chart means.

Is the last the same length as my foot?

No. The last is longer than the foot to leave room at the toe. That allowance is a design decision each brand makes per model, which is one reason two shoes with the same size number fit differently.

Which conversion should I trust?

The chart of the brand you are buying. The formulas describe how the systems are defined; brands round them, shift them and build on their own lasts.

Sources

Checked on 18 September 2026. Brand charts change: the linked page is the authority, not this one.

The formula column is arithmetic from the definitions above. The brand columns are copied from each brand's own published chart; nothing in them is interpolated.

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