Shoe Size Converter

A shoe size is a number on a scale, not a direct measure of your foot. Each region built its own scale, and the scales start at different points. This converter links them through one number you can measure yourself, the length of your foot.

What Shoe Size Conversion Measures

It changes the label, not the shoe. US men's 9, UK 8 and EU 42 all describe about the same shoe length in three scales. The tool does not know your foot width or how a brand cuts its shoes. Children's sizes use different scales and are not included.

The Formula

UK and US sizes count in barleycorns, an old unit equal to one third of an inch. Brannock marks its scales at 0.333 inch per size². European sizes count in Paris points, about two thirds of a centimeter². The inch is exactly 25.4 mm¹. With f as foot length in inches and F as foot length in cm, the common rules are⁶:

UK = 3 x f - 23

US men's = 3 x f - 22

US women's = US men's + 1.5 (retail pairing)

EU = 1.5 x F + 2.54

Australia men's = UK, Australia women's = US women's

Japan (JIS) = F rounded to the nearest 0.5 cm

The US men's rule matches the foot length column on Nike's men's chart to within 0.07 of a size⁵, and Brannock's US men's scale follows the same rule². The EU rule is the least settled: published versions add 2 (the ISO formula⁶) to about 3 (Nike's and Brannock's EU scales). This tool uses 2.54, the same two-barleycorn toe room as the UK and US rules.

How This Calculator Computes Your Result

Pick a starting point: foot length in cm or inches, or a size in any system. The tool converts it to foot length, then to every other system. Sizes round to the nearest half size, or up to the next half size if you choose that. The number you typed is never rounded. You can switch the US women's scale and see two Japan numbers (explained below). Adult foot lengths from 21.5 to 35 cm (about 8.5 to 13.8 in) are accepted.

What Your Result Means

The result is a size in every system for the same foot length. Here are common men's sizes worked out with the formulas above, with US women's on the retail pairing.

If your foot falls between sizes, many fitters suggest the larger one. Nike's chart says the same⁵.

How to Measure Correctly

You can do at home what a Brannock gauge does in a shop, with paper and a ruler.

• Measure late in the day. The American Podiatric Medical Association and Brannock both advise this³ ⁷.

• Wear the socks you plan to wear with the shoes.

• Stand on a sheet of paper, heel against a wall, weight on both feet so the foot spreads out fully³.

• Trace around your foot with the pen held upright. Mark the heel and the tip of your longest toe, which is not always the big toe³.

• Measure from the heel mark to the toe mark in cm.

• Do both feet and use the larger number³ ⁷.

• Do not add extra room. The size rules already allow for it, since a shoe is built on a form (the last) typically 13 to 25 mm longer than the foot⁶.

• When trying shoes on, look for a gap of about 10 to 20 mm between your longest toe and the end of the shoe⁸.

Why Charts Disagree

There is no official exact conversion. The ISO standard on size conversion says these systems grew up separately and offers its tables only as a guideline⁴. Brannock notes that variations exist within the same scale from one country to another². The main splits are:

• US women's sizes. The standard scale puts women's one size above men's. Many US retailers use one and a half⁶. Nike pairs men's 8 with women's 9.5¹⁰. The tool defaults to the retail pairing and lets you switch.

• Japan. The national standard (JIS) uses foot length in cm⁶. Brand charts often print a higher number for the same shoe, about men's size plus 18, which is roughly 0.5 to 1.5 cm above foot length for most adult sizes⁵. The tool shows both.

• EU. Brand sizes can sit above the formula. Nike lists men's 9 as EU 42.5⁵, and the formula gives 41.9.

• Within one brand. Nike's men's chart puts UK half a size below US for small sizes and a full size below from US 7 up⁵. Brannock's own UK scale sits half a size below US men's throughout². This tool uses a full size, as Nike does from US 7 up and as the ISO tables do⁶.

How Often People Wear the Wrong Size

In a UK study of 65 older patients on a rehabilitation ward, 47 (72%) wore ill-fitting shoes, meaning more than half a UK size off in length or more than one width fitting off⁹. A review of 18 studies found that 63 to 72% of participants wore shoes that did not fit the width or length of their feet, and linked poor fit to foot pain, corns, calluses and lesser toe deformity⁸. Most of this research is in older adults and other special groups, and studies define a wrong fit differently, so it is not a single figure for everyone.