Pick up three shoes and you find three different numbers on the sole. The same foot can be a UK 8, a European 42, a US 9 and a Japanese 27. The numbers don't agree, and none of them is a length you can read off with a ruler. So where do shoe sizes come from? The short answer is medieval barley farming, French export trade, industrial mass production, and a NATO supply problem.
First, a key idea: the last, not the foot
Before any of the systems make sense, one thing has to be clear. Most traditional shoe sizes don't measure your foot. They measure the last, the foot-shaped mould a shoe is built around. A shoe needs room past the toes, so the last is always longer than the foot inside it. That is why a size number never matches your foot length in centimetres, and why two brands can label the "same" size differently: they are describing their last, not you. Only the newest systems size the foot directly.
England and the barleycorn (1324)
The oldest system still in daily use is the British one, and it is built on a grain of barley. In 1324, King Edward II is said to have standardised the inch as the length of "three grains of barley, dry and round, placed end to end." That gives us the barleycorn: one third of an inch, about 8.47 mm.
English cordwainers took the barleycorn as their step size, and it stuck. One full UK shoe size still equals one barleycorn, a third of an inch of last length. The scale starts at a child's size 0, set at a last length of four inches (about a newborn's foot), and each size up adds one barleycorn. Children's sizes run to 13½, then the count resets: adult size 1 starts again at 8⅔ inches and climbs from there. That reset is why an adult UK 9 works out to 34 barleycorns of last length, even though the shoe says 9.
France and the Paris point
Continental Europe went metric, but in its own way. French shoemakers in the early 1800s built their scale on the Paris point (point de Paris): two thirds of a centimetre, about 6.67 mm. One Paris point is one full size, and it too measures the last rather than the foot.
Why two thirds of a centimetre, an oddly specific fraction? It is most likely a metric stand-in for an older unit. 2⅔ cm is very close to a quarter of a French inch, so the trade rounded its existing step into the new metric system. The Paris point became the continental standard, which is why you see it under so many names: European size, French size, German size, or just "EU". It also explains why continental sizes have no half sizes. The two-thirds-of-a-centimetre step is already small enough that half steps were never needed.
The United States: the same barleycorn, shifted
American sizing grew straight out of the English one. When New York businessman Edwin B. Simpson set out a detailed US system in the 1880s, he took the British barleycorn scale (one third of an inch per size, measuring the last) and picked a different starting point. That is why UK and US numbers run parallel but about a size apart instead of matching.
It also explains the quirk that men's and women's US sizes differ for the same foot. You can turn a foot length into a US size by multiplying by three and subtracting a fixed number: 22 for men, 21 for women. That one-unit offset is a leftover of how the two scales were first set up, not a difference in feet.
Japan and Mondopoint: sizing the foot at last
Everything above measures the last. Two systems break that habit and measure the foot directly, in plain metric length.
Japan's system, standardised as JIS, is the simplest in the world: your size is your foot length in centimetres. A 27 cm foot is a size 27, for men, women and children alike, with half-centimetre steps between. Measure your foot and you have your size.
The international version of that idea is Mondopoint (from mondo, "world"), now defined in ISO 9407. It gives size as foot length in millimetres, and often foot width too, so the marking describes the actual foot a shoe should fit. The reason it exists is practical. In the 1970s NATO had to supply boots to soldiers from many countries, and the clash of national systems was a headache. One unambiguous measurement fixed it. Outside the military, Mondopoint's most familiar home is ski boots, where an exact foot length matters far more than a fashion number. That is why ski boots are sold in "mondo" sizes.
The systems side by side
| System | Measures | Step per size | Origin |
|---|---|---|---|
| UK | The last | 1 barleycorn (⅓ inch, ~8.47 mm) | England, standardised 1324 |
| US | The last | 1 barleycorn (⅓ inch) | Based on UK; formalised 1880s |
| EU (Paris point) | The last | ⅔ cm (~6.67 mm) | France, early 1800s |
| Japan (JIS) | The foot | Foot length in cm | Japanese Industrial Standard |
| Mondopoint (ISO 9407) | The foot | Foot length in mm | NATO / military, 1970s |
What the sizes really tell us
A shoe size was never meant to be an exact measurement of your foot. It is a label for a mould, inherited from barley grains and export ledgers, then rounded, reset and shifted across centuries and borders. That is why the same person honestly fits different numbers in different brands and countries, and why "just tell me my size" has no clean answer.
The trend, from Japan's foot-length sizing to Mondopoint, runs toward measuring the real foot instead of a mould. Custom orthopedics takes that further. Instead of fitting a person to the nearest number on a centuries-old scale, we 3D-scan the individual foot and design around its real shape. When an insole is built from a scan of your foot, the number on the label finally stops mattering. Read more about why 3D scanning is the future of orthopedic measurement.
