Shoe size conversion calculator
Shoe sizing is a linear function of foot length in every system, with different origins and step sizes. That makes it convertible, if not consistent.
EU size
42.0
- UK size
- 8.1
- US size
- 9.1
- US men's size
- 9.1
- US women's size
- 10.6
- Foot length in centimetres
- 27.0
- Foot length in inches
- 10.63
Show the working
- Foot length = 270
- Sizing = 1
- Fitting allowance = 10
- last_length = 270 + 10 = 280
- UK size = 280 / 8.46666666666667 - 25 = 8.070 87
- US men's size = 8.070 87 + 1 = 9.070 87
- US women's size = 8.070 87 + 2.5 = 10.5709
- US size = 1 > 0 ? 9.070 87 : 10.5709 = 9.070 87
- EU size = 280 / 6.6666666666667 = 42
- Foot length in centimetres = 270 / 10 = 27
- Foot length in inches = 270 / 25.4 = 10.6299
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- UK size = (foot length + allowance) in barleycorns - 25, where a barleycorn is 1/3 inch
- EU (Paris point) size = last length in mm / 6.667, a Paris point being 2/3 cm
The UK scale is built on the barleycorn, one third of an inch, which is a genuine historical unit and one of the odder survivals in measurement.
Manufacturers vary by half a size or more. Use this to narrow the search, not to buy without trying.