Length is only half the equation. The debate between US 8.5 and 9 often comes down to width rather than longitudinal millimeters.
Standard European footwear is built on an average medium width profile, roughly equivalent to a US Women's B width or US Men's D width. Unlike American makers, European factories rarely offer designated narrow (AA/A) or wide (D/EE) options in their off-the-shelf catalog. When a consumer with a wide foot buys a European shoe, they cannot choose a wider width. They are forced to step up in length to gain interior volume.
If your foot measures 24.8 centimeters in length but features a wider ball circumference, an EU 39 labeled as a US 8.5 will pinch your metatarsals. In that scenario, moving to an EU 40 (US 9 or 9.5) provides the necessary lateral space, even though the shoe leaves slight excess room in front of the toes. Conversely, narrow feet swim inside wide-toe European casual shoes, making an EU 39 feel uncomfortably loose.
