Use this when you need to take a real foot measurement into a retailer or brand chart and decide which published size range actually contains your longer foot.
What this tool is actually telling you
ISO 19407:2023 bases conversion tables on foot length across major systems, but shoe lasts, width, toe shape and brand grading still influence fit.
Use this as measurement-based guidance, not a guarantee of fit. Brand blocks, grading, fabric stretch, construction and personal preference can change the best size.
Inputs that make the answer stronger
- Measure both feet while standing when practical and use the longer relevant measurement.
- Keep foot length separate from shoe internal length and from a printed size number.
Worked example
A foot-length measurement gives a more stable cross-system anchor than assuming every EU 42 or US 9 is physically identical across brands.
How to use the result for a real decision
Use the longer foot as the chart reference, enter the adjacent brand rows you are choosing between, and resolve any boundary with the retailer’s own fit notes rather than a universal conversion table.
Why the same shoe size can fit differently
Foot length is a strong cross-system anchor, but width, toe shape, last geometry, upper material and the brand’s own grading still change the final fit.
Sources and verification
Footwear claims use current footwear sizing references where applicable, while final brand fit remains tied to the retailer’s own chart and product construction.
Questions people ask
Why can two shoes in the same size fit differently?
Size numbers do not fully describe last shape, width, toe box, materials or brand grading.
Is foot length better than converting a remembered size?
Usually yes for cross-system comparison because ISO conversion guidance is anchored to foot length.