How UK and US Shoe Sizes Differ
Both the UK and US shoe sizing systems are based on barleycorn units, where one size equals one third of an inch (approximately 8.47 mm) of foot length. The two systems use different starting points, which creates a fixed offset between them.
For men's footwear, US sizes run half a size larger than UK sizes (US = UK + 0.5). For women's footwear, the offset is larger: US sizes run two full sizes above UK sizes (US = UK + 2). Children's sizes follow the same offset as men's (US = UK + 0.5).
These offsets have been consistent for decades and are used by virtually all major footwear brands including Nike, Adidas, New Balance, and Clarks when publishing their size guides.
Worked Example
A UK men's size 9 shoe converts as follows:
- US men's size: 9 + 0.5 = 9.5
- EU size (approx): 42-43
- Approximate foot length: 27.5 cm
This matches the default output of the converter above with gender set to Men's and UK size 9 selected.
EU Sizes Explained
EU (European) shoe sizes are measured in Paris points, where each size equals two thirds of a centimetre. EU sizes are technically unisex (the same number applies to both men and women for the same foot length), but women's lasts are typically narrower and shorter, so a woman buying EU 40 will usually find that shoes designed for women in EU 40 fit differently to men's shoes in the same number.
The approximate formula is: EU size = (foot length in cm + 1.5) / (2/3), which simplifies to EU = (foot length cm × 1.5) + 2.25. In practice, brand-specific lasts mean EU sizes can vary by half a size between brands.
Measuring Your Foot
For the most accurate result, measure your foot length at the end of the day when feet are at their largest. Stand on a piece of paper, trace around your foot, and measure from the heel to the tip of the longest toe. If your two feet differ in size, use the measurement from the larger foot. Round up to the next half size if you are between sizes.
Foot width also matters: standard width is D (men's) or B (women's). Wide-fit shoes are available in E (men's) or D (women's). If you find standard shoes tight across the ball of the foot, consider a half size up or a wide-fit style.
Online Shopping Tips
When ordering shoes from UK retailers such as ASOS UK, Next UK, or Marks and Spencer, the sizes listed are UK sizes. When ordering from US retailers such as Zappos, Nordstrom, or DSW, the sizes listed are US sizes. Always check the size guide on the product page, as some international brands publish their own conversion charts that may differ slightly from the standard offsets above.
New Zealand retailers typically follow UK sizing, as New Zealand's retail history has closer ties to the UK than the US. If you see a size with no country label on a NZ website, assume it is a UK size.
Related Converters
Sources and method: Brannock Device Company sizing standards. ISO/TS 19407:2015 Footwear (shoe size designation). Conversion offsets verified against published size guides from Nike, Adidas, New Balance, Clarks, and Ecco. EU sizes derived from Paris point formula (1 Paris point = 2/3 cm).
Shoe size conversions are approximate. Sizing varies between brands and even between styles from the same brand due to differences in last shape and construction. Always consult the brand's own size guide and check the retailer's returns policy before purchasing footwear online.
