Why Your Shoe Size Is a Different Number Abroad

Why does a single foot need four different numbers to describe it? Buy the same pair of sneakers in London, then Paris, then Tokyo, and the box says something different every time: UK 9, European 43, Mondopoint 270, despite fitting the exact same foot. None of the numbers is wrong. They're just measuring it with three different rulers that never agreed to talk to each other.

The confusion is not a manufacturing accident or a marketing quirk. It's inherited from measuring systems that predate the modern shoe industry by centuries, according to a history of footwear sizing published by SATRA, the British footwear-testing and standards body.

A medieval grain became the industry standard

The starting unit for both British and American shoe sizes is the barleycorn, literally, a dried kernel from the barley plant, judged to be about a third of an inch long. England formalized the barleycorn as a measurement unit in a statute dated to somewhere between 1266 and 1303, and in 1324, King Edward II made it official under pressure from merchants tired of arguing over inconsistent measurements: three barleycorns to the inch, 12 inches to the foot, per SATRA.

Shoemakers adopted the barleycorn increment for sizing, and it never left. Even today, a UK or US shoe size moves up one full size for every extra third of an inch of last length, a unit borrowed from a grain of barley in 14th-century England, still governing what fits on your feet.

Somewhere in that history, the size numbers also produced a genuine mystery: why do children's shoe sizes in the UK and US run from roughly 0 to 13, then start over at 1 for adults? SATRA describes two competing legends, and is careful to note neither is confirmed. One holds that early English shoemakers started children's sizing at four inches, roughly a "hand," the same unit used to measure horse height, then added a nine-inch "span" to mark where adult sizing should begin, landing on 13 as a natural cutoff. The other suggests it's simpler: a 12-inch ruler has 13 marks if you count the zero, and someone, at some point, built a sizing system around that instead. "These ideas for the source of the 13 sizes of children's shoes may well be fanciful," SATRA concludes, "with the true reason having been lost in time."

The measuring tools got more scientific long before the numbering system did. The wooden "Ritz Stick," patented in 1916, became the first widely used foot-measuring device in the US. A New York inventor named Charles Brannock spent two years improving on it, patenting his own device in the 1920s and founding the Brannock Device Company to manufacture it: the same metal foot-measuring tool, with its sliding arch indicator, still bolted to the floor of shoe stores today. Brannock ran the company until his death in 1992, at 89; a buyer named Salvatore Leonardi purchased it from his estate the following year and still manufactures it, according to SATRA.

Continental Europe built its own system from the metric revolution

While Britain and the US kept counting barleycorns, continental Europe hitched its shoe sizes to the birth of the metric system itself. The "Paris point," two-thirds of a centimeter, became the base unit for what's now called the continental system, used across most of mainland Europe and parts of Latin America. Brazil uses the same continental method but subtracts two from the final number, a quirk confirmed independently by both SATRA and Wikipedia's technical entry on shoe sizing.

A third system, Mondopoint, arrived far more recently: introduced in the early 1970s under international standard ISO 2816:1973 as an attempt to unify the mess. It measures a foot directly in millimeters rather than assigning an arbitrary size number, which is why a men's UK size 9 is labeled, plainly, "270" under Mondopoint, 270 millimeters of foot. Rather than replacing the older systems, Mondopoint simply became a fourth one; it's now the primary standard across China, Japan, Russia and the former Soviet republics, and is also used by NATO for military footwear, per SATRA and Wikipedia.

Conversion values per the International Organization for Standardization's shoe-size tables, cited in Wikipedia's shoe size entry.

Manufacturers have mostly given up trying to pick a winner. Sports shoe labels since the early 2000s routinely print all four numbers (EU, UK, US and Mondopoint) on the same box, a tacit admission that eight centuries after King Edward II's barleycorn decree, nobody has managed to retire the other three systems. The next traveler squinting at a shoe-store wall in a foreign country isn't doing the math wrong. The industry itself never finished doing it.