For most suits, button the jacket while standing and unbutton it when sitting. On a two-button suit , fasten only the top button ; on a three-button suit , fasten the middle button , optionally the top button too, and never the bottom one.

Quick rules

  • Single-breasted, 1 button: Button it when standing, unbutton when sitting.
  • Single-breasted, 2 buttons: Button the top button only; leave the bottom button undone.
  • Single-breasted, 3 buttons: “Sometimes, always, never” — top is optional, middle is always, bottom is never.
  • Double-breasted: Usually keep it buttoned when standing; styles vary, but the jacket is generally meant to stay more closed.

Easy memory trick

  • Top = yes sometimes
  • Middle = yes
  • Bottom = no

One exception to know

If you’re wearing a vest/waistcoat , the usual suit-jacket rules still apply to the jacket, but the vest often follows its own convention, with the bottom button typically left undone.

If you want, I can also give you a super short “what to button” cheat sheet for 1-, 2-, 3-, and double-breasted suits.