Every shoe brand has its own chart. The same EU 43 can map to different foot lengths depending on the manufacturer. That is why Unisizer does not rely on the label alone: it extracts the canonical measurement behind it — foot length.
Once we have that base measure, sizes can be compared fairly across brands, because the comparison no longer depends on the printed number on the box. This is especially useful when switching between sport and everyday footwear.

If your favorite brand size is already proven in real wear, this flow is often more convenient than entering foot length directly. It moves your familiar reference point into a new brand chart quickly.