What is the average shoe size worldwide?

There is no global survey of shoe sizes. Foot-measurement studies in Europe and North America put the average adult male foot at about 26 to 27 cm (roughly EU 42 to 43) and the average female foot at about 23 to 24 cm (EU 38 to 39). Foot length runs at about 15% of height, so 6 to 7 cm of extra height adds roughly 1 cm of foot.

Source: Jurca et al. (2019), Footwear Science; Hawes & Sovak (1994), Ergonomics