Three systems, three starting points
A "size 9" means nothing until you know which system it belongs to. The US, UK, and European systems were developed independently, and each one counts from a different zero point using a different step size — which is why the same foot gets a different number depending on where the shoe was made.
| System | Step per full size | Based on |
|---|
| US | ≈8.47 mm (⅓ inch) | Barleycorn; separate men's and women's scales |
| UK | ≈8.47 mm (⅓ inch) | Barleycorn, but starting from a different zero point |
| EU | ≈6.67 mm (⅔ cm) | Paris point; one scale meant to cover everyone |
US and UK sizes step in exactly the same increments — they just start counting at different places. The EU step is smaller (6.67 mm versus 8.47 mm), which is why EU numbers look so much bigger and why converting between EU and the other two never lines up perfectly: a one-size jump in the US or UK is a bit more than a one-size jump in Europe.
The rules of thumb
- US men's → UK: subtract about 0.5 to 1. A US men's 9 is roughly a UK 8 to 8.5.
- US women's → UK: subtract about 2. A US women's 8 is roughly a UK 6.
- US women's ↔ US men's: women's sizes run about 1 to 1.5 higher for the same foot, so a women's 8.5 is roughly a men's 7.
- US men's → EU: add about 33. A US men's 9 is roughly EU 42.
Retailers disagree on some of these conversions by half a size — for example, whether the men's US-to-UK gap is 0.5 or 1. That isn't an error on anyone's part; it's a sign that the systems don't convert cleanly. Treat every chart as an approximation.
Men's size chart (approximate)
| US men's | UK | EU | Foot length |
|---|
| 7 | 6 | 40 | ≈25.0 cm |
| 8 | 7 | 41 | ≈26.0 cm |
| 9 | 8 | 42 | ≈27.0 cm |
| 10 | 9 | 43 | ≈28.0 cm |
| 11 | 10 | 44 | ≈29.0 cm |
| 12 | 11 | 45 | ≈30.0 cm |
Women's size chart (approximate)
| US women's | UK | EU | Foot length |
|---|
| 6 | 4 | 36–37 | ≈23.0 cm |
| 7 | 5 | 37–38 | ≈24.0 cm |
| 8 | 6 | 38–39 | ≈25.0 cm |
| 9 | 7 | 39–40 | ≈26.0 cm |
| 10 | 8 | 40–41 | ≈27.0 cm |
| 11 | 9 | 41–42 | ≈28.0 cm |
Notice the trap built into these two tables: the same 25 cm foot is a US men's 7 but a US women's 8 to 8.5, depending on the brand. Ordering unisex sneakers listed only in men's sizes is where most women's-to-men's mix-ups happen.
Why foot length beats size labels
The only measurement that means the same thing everywhere is your actual foot length in centimeters. Japan and Korea size shoes directly this way, and most brands publish a centimeter column in their own charts. To measure:
- Stand on a sheet of paper with your heel against a wall and your full weight on the foot.
- Mark the tip of your longest toe (it isn't always the big toe) and measure from the wall to the mark.
- Measure both feet, preferably late in the day when they've swelled slightly, and use the larger number.
- Match that length to the centimeter column in the specific brand's own size chart rather than a generic one.
Other things that change the fit
- Brand and shoe shape. Two shoes with the same printed size can differ by half a size or more depending on the last (the mold the shoe is built around).
- Width. US shoes come in letter widths — narrow, standard, wide, extra wide — while European shoes usually don't offer widths at all. A shoe that's the right length but too tight across the ball of the foot is a width problem, not a size problem.
- Running shoes run bigger. Feet swell over a long run, so runners commonly size up about half a size from their everyday shoes and leave roughly a thumb's width of space in front of the longest toe.
- Feet change over time. Arches flatten and feet lengthen gradually with age, so the size you've worn for a decade isn't necessarily still the right one.
Converting the measurement itself
If a size chart gives foot length in inches and you measured in centimeters (or the reverse), the Length category on the UnitDial converter handles the arithmetic — 1 inch is exactly 2.54 cm.