In 2026, the global footwear industry still uses a unit of measurement from 1324. There's a better way. It already exists. Almost nobody uses it.
Not because feet are complicated.
Because the systems measuring them are absurd.
A foot that's 27 centimetres long — a simple, measurable fact — gets translated into a different arbitrary number depending on where you buy your shoes.
Japan just uses the length of your foot. That's it.
King Edward II decrees that three barleycorns — dried kernels of barley, roughly 8.47mm each — equal one inch. The measurement is ancient, but the formalisation is new. Shoes aren't mentioned.
Randle Holme III publishes the first documented shoe sizing system. Children's sizes run 0–13, then adults restart at 1. Each size is one barleycorn apart. Why 13? Nobody knows.
French shoemakers invent the Paris Point: each size = ⅔ centimetre. It becomes the European system. It measures the shoe mould, not the foot — which causes its own problems.
The US copies the British barleycorn system, but shifts the starting point by 1/12 of an inch. US sizes now run roughly one number larger than UK for the same foot. Nobody can explain why.
Charles Brannock, a university student, builds a foot-measuring device from an Erector Set in his fraternity house. It measures three dimensions. It's still used in shoe shops today — almost 100 years later.
Mondopoint is created. The ISO develops a metric system: measure your foot in millimetres, that's your size. Length and width. No conversion tables. NATO adopts it immediately.
Consumer shoe brands still haven't adopted it. We're still using barleycorns.
RunRepeat measured the internal length of shoes all labelled US men's 9. Within a single brand — Adidas — the actual internal length varied by over 20mm. That's more than two full sizes of difference.
All labelled "US 9." Actual internal length varies by 18mm.
A single pair of running shoes generates 13.6 kg of CO₂ — a week's worth of a lightbulb. Return it, and that footprint doubles.
It's called Mondopoint. Developed by the ISO in the 1970s. It measures your foot in millimetres. Your foot is 270mm long and 100mm wide? Your size is 270/100.
No conversions. No gendered offsets. No barleycorns. One number, worldwide.
It's not theoretical. It's already in use:
NATO uses it for all military boots.
Every ski boot in the world is sized in centimetres.
Japan uses centimetres as its primary consumer system.
South Korea uses millimetres — size 260 means a 260mm foot.
China adopted Mondopoint via national standard.
Vanity sizing. Research shows smaller size numbers boost self-esteem. "I'm a size 7" is an identity statement, not a measurement. Centimetres would make that game transparent.
Manufacturing inertia. Every brand's shoe moulds are proprietary. Changing them means coordinating factories across China, Vietnam, and Indonesia. It's expensive — and nobody wants to go first.
Cultural resistance. Only three countries haven't officially adopted the metric system: the US, Myanmar, and Liberia. Yet we already buy wine in 750ml bottles and dose medicine in milligrams.
Retail incentives. Confusing sizing means more try-ons, more bracketing, more visits. Some brands benefit from the chaos.
Railroads
In 1886, American railroads operated on 23 different track widths. Freight had to be unloaded and reloaded at every junction. On a single day — June 1, 1886 — 13,000 miles of track were converted to standard gauge. Overnight.
Shipping Containers
Before standardised shipping containers in 1956, loading cargo cost $5.86 per ton. After: 16 cents. The inventor released his patents royalty-free so every container in the world would fit every ship.
USB-C
In 2022, the EU mandated USB-C as the universal charging connector, ending 30 years of cable chaos. The argument? Environmental waste.
Measure your foot. That number is your size. No chart. No conversion. No barleycorns.
Your foot is probably around
Stand on paper. Mark your heel and longest toe.
Measure the distance. That's it. That's the whole system.
The standard exists — ISO 9407. The technology exists. Billions of people already use it. We're just waiting for everyone else to stop measuring feet in medieval grain.