Understanding UK to US Shoe Size Conversion
UK and US shoe sizes both grew out of the same historical "barleycorn" measuring system, but each country kept counting from a different starting point — and men's, women's, and children's shoes even use different starting points within the same country. The result is that there is no single number you add to every UK size to get a US size; the correct offset depends on whether you are converting a men's, women's, or kids' shoe.
The standard conversion formula
The offsets below are the widely published rule of thumb used by most footwear retailers and size charts:
- US Men's size = UK size + 1 — a UK 8 is a US Men's 9.
- US Women's size = UK size + 2 — a UK 8 is a US Women's 10.
- US Kids'/Youth size = UK size + 0.5 — a UK 8 is a US Kids' 8.5.
This calculator applies whichever offset matches the category you select, adds it to the UK size you enter, and also rounds the result to the nearest whole US size, which is useful when a half size is not stocked.
Why the offset differs by category
Historically, UK sizing schemes for men, women, and children each start counting from a different reference foot length, and the US schemes do the same. Because the starting points do not line up the same way between the two countries for every category, a UK size number does not carry a fixed "+X" relationship to its US counterpart across men's, women's, and kids' shoes — each needs its own offset.
How to get the best results
- Confirm you are entering a UK size, not a US, EU, or centimeter measurement.
- Pick the correct category — the same UK number converts to a different US size for men's, women's, and kids' shoes.
- Treat the result as a starting point: brand, shoe last, and width still affect real-world fit, so check the specific brand's chart if you are between sizes.
Practical context
This offset-based conversion is a widely used approximation, not a legally standardized formula — shoe sizing is not internationally regulated the way, for example, clothing measurements sometimes are. Use the converted size as a reliable starting point, and when ordering from an unfamiliar brand, cross-check against that brand's own size chart or try the closest half size on either side.