Boots

Boots are built on their own last (the physical form the shoe is shaped around), which is often different from the last a brand uses for its sneakers or dress shoes — so a size that's correct in one category from a given brand isn't a reliable guide to the same brand's boot sizing. Checking a brand's boot-specific size guidance, rather than assuming consistency with its other footwear, matters more here than in most categories.

For any boot with a shaft — ankle, mid-calf, or knee-high — width around the calf or ankle is a fit dimension sneakers simply don't have, and it isn't captured by the shoe size at all. A knee-high boot can be the correct length size and still not zip or sit correctly if the shaft circumference doesn't match, which is why some brands publish a separate calf measurement worth checking before ordering.

Material affects break-in more than it does with sneakers: genuine leather stretches and softens with wear in a way synthetic uppers mostly don't, so a leather boot that feels snug across the top of the foot in the first days can ease noticeably after a few wears, while a synthetic boot in the same snug fit will generally stay that way.