Read the system
Check whether a label uses US, UK, EU or another system, and which category the chart covers. Use the chart for the exact manufacturer and product. Do not assume a conversion is identical across every label or silhouette.
Compare real measurements
For footwear, follow the maker’s measuring instructions and consider width as well as length. For clothing, compare laid-flat garment measurements with a piece that fits you well. A chest width, rise or sleeve measurement gives information a generic small or large label cannot.
Try it in context
Wear the socks or layers you plan to use and move normally when trying a piece. Styling preferences and comfortable fit are personal. This page offers comparison steps rather than a universal size conversion chart.