Use the seller's measurement method
Follow the brand's instructions for measuring your feet, including whether it asks for heel-to-toe length and how it converts that measurement to a size. Measure both feet and use the guidance for the larger measurement. If the guide is unclear, ask rather than rounding towards the size left in stock.
Check width as well as length. A narrow shoe in a larger size may still be the wrong shape, while a wide-fit description needs to be understood in the context of the range. Look for details about the toe shape, fastening and materials that affect how the shoe accommodates your foot.
Try them for the intended use
When trying on the shoes, wear the kind of socks or hosiery you plan to use. Fasten them properly and walk indoors on a clean surface while following the seller's try-on conditions. Pay attention to heel movement, pressure across the forefoot and whether your toes have the space described by the brand's fitting advice.
Do not buy a clearly uncomfortable pair on the assumption that it will stretch into the right size. Materials behave differently, and a hoped-for change is not a reliable fit plan. If you use prescribed insoles or have specific fitting needs, make those requirements part of the comparison and seek appropriate fitting help.
Check return postage, the return window and any packaging requirements before ordering. Buying two sizes to compare can temporarily tie up more money and may create return costs, so factor that into the decision. Keep the model name, size and width of pairs that fit well, but recheck when changing styles. A sale is useful when your size is available, not when the remaining size persuades you to disregard the fit.
