Most Nike sneakers run about a half size small compared to other major brands. The recommendation across most models: order a half size up from your usual.
Air Force 1, Dunks, and Air Max all consistently fit small. Jordans (especially Jordan 1) fit true to size for most people but slightly large in the toe box.
Running shoes (Pegasus, Vomero, Invincible) tend to fit true to size — Nike designs running models with more accurate lasts.
Width matters: Nike's standard width is narrow compared to New Balance or Hoka. If you have wide feet, look for 'Wide' or '4E' options.
When in doubt, order both sizes and return the one that doesn't fit. Free returns make this risk-free.