Why Shoe Sizes Differ Between Countries

The barleycorn — England, 1324

King Edward II standardized the inch as three barleycorns laid end to end. Cordwainers picked up the smallest unit and used it as the increment between shoe sizes. A full size = 1/3 inch = one barleycorn. That's the ancestor of every US and UK size still sold today.

The Paris Point — France, 1800s

Continental Europe rejected the imperial system and standardized on 2/3 of a centimeter (6.67 mm) per size. It's linear, metric-friendly, and covers infants to adults on a single scale — the reason a European chart runs from EU 16 to EU 50.

Mondopoint — international standard, 1970s

The ISO standard (ISO 9407) proposed the obvious solution: state foot length in millimeters. Mondopoint sizes are just numbers like 265, 270, 280 — literally the length of the foot in millimeters. Japan and Korea adopted it wholesale; ski boots and military footwear use it globally. Fashion mostly ignored it.

Why brands still disagree

Even within one system, a size 9 varies. A shoe size is nominally the length of the last (the shoe-shaped mold) plus an allowance for movement inside the shoe. Different brands use different allowances — 0.75 to 1.5 cm — because their target fit is different. A dress shoe expects less internal movement than a running shoe. Neither is 'wrong', but the numbers on the label diverge.

The vanity sizing pull

Athletic brands rarely inflate shoe sizes the way apparel brands inflate clothing sizes. But there's a subtler drift: as customer feet have gotten longer on average, brands have quietly widened lasts and softened toe boxes, so today's 'US 10' fits with more air than it did in 1990. The chart didn't move — the shoe did.

What to do about it

• Ignore the label until the end. Start with foot length in cm.
• Look up the specific brand's own conversion, not a generic one.
• Read recent reviews for that model — half-size-large is a real signal.
• For borderline sizes, buy from a retailer with free returns.