What is On US 8.5 in EU?

About EU 42 on the On reference chart (UK 8, ~25.8 cm). Confirm the model fit guide.

Is On EU 42 the same as every brand?

No. EU labels can map to slightly different foot lengths. Match by cm, then adjust for the specific model.

Measure heel-to-longest-toe in cm, then use the cm converter and read the model page for width/last quirks.

Chart-matched conversion for a high-intent size query — then check the model last.

From brand_charts.csv — foot-length cm is the match key.

Chart labels are not lasts. Open a On guide before you buy:

Cloudmonster (true to size) · Cloud 5 (runs small) · Cloudsurfer (true to size)

Other on sizes: US 7 · US 7.5 · US 8 · US 9 · US 9.5 · US 10

What is On US 8.5 in EU?: About EU 42 (UK 8, ~25.8 cm). Confirm the model guide.
How do I convert by foot length?: Measure in cm, then open the cm converter or foot-length guide.