Ordering shoes across borders is where sizing systems collide: US sites use US sizes, European brands use EU sizes, and running brands increasingly publish foot length in millimeters. This converter puts all three (plus UK) side by side, separately for men and women — because the same number means different lengths in each system.
How to measure your foot
Measure in the evening, when feet are slightly swollen. Stand on a sheet of paper with your heel against a wall, mark the tip of your longest toe, and measure the wall-to-mark distance in millimeters. Measure both feet and size to the larger one. For sneakers add 5–8 mm of wiggle room; for dress shoes about 5 mm.
The rough relationships
Your foot length in millimeters is the modern Chinese sizing (a 250 mm foot wears "250"). EU size ≈ (foot length in cm) × 1.5 + 2 roughly — or use the chart. Men's US ≈ EU − 33 (EU 40 → US 7), UK ≈ US − 1. Women's US ≈ EU − 31. These are approximations; brands vary.
Why brands differ by half a size
The charts give industry-standard approximations, but each brand's last (the mold shaping the shoe) differs. Nike and Adidas commonly run a half size small; Clarks and other English brands often run large. Before ordering online, search "brand + size run small or large" and combine that with this chart.