Three systems, three units
US sizes are based on the barleycorn, one third of an inch, with separate scales for men, women, and children. UK sizes use the same base unit but a different starting point, which is why UK numbers run about one size below US men's. EU sizes use the Paris point, two thirds of a centimeter, and are usually written as a whole number.
Because the systems use different increments, there is no single formula that converts all sizes perfectly. Conversion charts are approximations, and the only reliable anchor is your foot length in millimeters.
Why men's and women's numbers differ
A men's US 9 and a women's US 9 are not the same physical length. Women's sizes are typically offset by about 1.5 to 2 sizes from men's, so a women's 9 corresponds to roughly a men's 7 or 7.5. This is why the same number maps to EU 42 in the men's chart and EU 39–40 in the women's chart on our size pages.
Children's sizes continue the scale downward and eventually switch to youth sizing. Always check which profile a chart uses before converting — the number alone is ambiguous.
Paris points and the 240 question
EU sizing uses the Paris point, equal to two thirds of a centimeter of foot length plus an allowance. This is why a foot length of 240 mm corresponds to about EU 38: the number printed on the shoe is not the foot length itself, but a scale derived from it. Chinese sizing often prints the foot length directly, which is why “240” appears in searches alongside EU sizes.
Mondopoint, described in ISO 9407, is a cleaner system that uses foot length in millimeters directly. It has never replaced national systems in retail, but it is the basis for many athletic-brand size charts.
How to measure your foot
Stand on a sheet of paper with your heel against a wall, wearing the socks you plan to use. Mark the tip of your longest toe and measure from the wall to the mark in millimeters. Measure both feet and use the larger result, ideally late in the day when feet are slightly larger.
Add a small allowance for toe room — roughly 5–10 mm depending on the shoe type. Athletic shoes usually need more room than dress shoes. Compare that total with the foot-length column of a size chart rather than converting through two or three size systems.
Why brands still vary
Last shape, width, and upper material all affect fit even when the length matches. A running shoe with a roomy toe box can fit a half size differently from a narrow dress shoe. Size charts describe length, not volume, so width and instep remain personal variables.
Use the chart as a starting point, then check the brand's own fit notes and return policy. For online shopping across borders, buying two adjacent sizes and returning one is often more reliable than trusting a conversion table alone.
Foot length to common labels
Measuring your foot in millimetres gives you a stable starting point that does not depend on which numbering system a brand uses. The conversions below are approximate because width and last shape still vary, but they place you in the right part of every chart.
- 240 mm ≈ EU 38 · US women's 7–7.5 · US men's 6
- 250 mm ≈ EU 40 · US women's 8.5–9 · US men's 7.5
- 260 mm ≈ EU 41–42 · US women's 10 · US men's 8.5–9
- 270 mm ≈ EU 43 · US women's 11.5 · US men's 10
- 280 mm ≈ EU 44–45 · US men's 11–11.5