Quick answer: A men's EU 42 fits a foot of about 26.7 cm, which is UK 8.5 and US 9.5.
How it's calculated
Every system counts in steps on the length of the shoe last, which is a little longer than the foot. EU (Paris point) sizes step by 2/3 cm: EU = 1.5 × foot length (cm) + 2. UK and US sizes step by one barleycorn, 1/3 inch.
From foot length in inches: UK adult = 3 × foot − 23 and UK child = 3 × foot − 10; US men = 3 × foot − 22, US women = 3 × foot − 21 (one size above men), US child = 3 × foot − 9¾. Results are rounded to the nearest half size. Some charts put UK children's sizes a full size below US; by these definitions the gap is only about a third of a size, so the two often round to the same number.
Mondopoint (ISO 9407), used for ski boots and military footwear, is simply the foot length in millimetres.
Worked examples
- Men's EU 42: foot ≈ 26.7 cm → UK 8.5, US 9.5
- Women's foot of 24 cm: EU 38, UK 5.5, US 7.5
Men's sizes
| Foot length (cm) | EU | UK | US |
|---|---|---|---|
| 24.5 | 39 | 6 | 7 |
| 25 | 40 | 6.5 | 7.5 |
| 25.5 | 40 | 7 | 8 |
| 26 | 41 | 7.5 | 8.5 |
| 26.5 | 42 | 8.5 | 9.5 |
| 27 | 43 | 9 | 10 |
| 27.5 | 43 | 9.5 | 10.5 |
| 28 | 44 | 10 | 11 |
| 28.5 | 45 | 10.5 | 11.5 |
| 29 | 46 | 11.5 | 12.5 |
| 29.5 | 46 | 12 | 13 |
| 30 | 47 | 12.5 | 13.5 |
Women's sizes
| Foot length (cm) | EU | UK | US |
|---|---|---|---|
| 22 | 35 | 3 | 5 |
| 22.5 | 36 | 3.5 | 5.5 |
| 23 | 37 | 4 | 6 |
| 23.5 | 37 | 5 | 7 |
| 24 | 38 | 5.5 | 7.5 |
| 24.5 | 39 | 6 | 8 |
| 25 | 40 | 6.5 | 8.5 |
| 25.5 | 40 | 7 | 9 |
| 26 | 41 | 7.5 | 9.5 |
| 26.5 | 42 | 8.5 | 10.5 |
| 27 | 43 | 9 | 11 |
Children's sizes
UK children's sizes run from 0 to 13½, then continue with adult size 1.
| Foot length (cm) | EU | UK | US |
|---|---|---|---|
| 12 | 20 | 4 | 4.5 |
| 13 | 22 | 5.5 | 5.5 |
| 14 | 23 | 6.5 | 7 |
| 15 | 25 | 7.5 | 8 |
| 16 | 26 | 9 | 9 |
| 17 | 28 | 10 | 10.5 |
| 18 | 29 | 11.5 | 11.5 |
| 19 | 31 | 12.5 | 12.5 |
| 19.5 | 31 | 13 | 13.5 |
Frequently asked questions
Is a UK size the same for men and women?
Yes, UK sizes are unisex. US sizes are not: a US women's size is about one size larger than the US men's size for the same foot (1½ in some brands).
How do I measure my foot?
Stand on paper with your heel against a wall, mark the tip of your longest toe and measure in cm. Measure both feet and use the longer.
Why do brands differ?
The standard formulas fix the sizing steps, but each maker chooses its own last shape and allowance, so the same number can fit differently.
Should I size up if I'm between sizes?
Usually, yes, especially if your feet are wide or it's a trainer. Some brands also make wide fittings. And try shoes on later in the day, when your feet are at their biggest.
What is Mondopoint?
Just your foot length in millimetres. It's used for ski boots, military boots and some work shoes, so a 265 boot fits a 265 mm foot.
Do children's sizes use the same scale?
No. UK and US kids' sizes have their own scale that runs up to about 13, then sizing starts again at 1. Pick the child group in the calculator.