The waist button is the button on your suit jacket that is traditionally placed at your waist by a tailor. Now it may not be “exactly” at your natural waistline, which is about 2 inches above your belly button, because each tailor measures just a tad bit differently. But this is where the button receives its name. So that means that while you are standing:

• In a three button suit– You button the middle button only, or the top two buttons. Do not ever button the bottom one.
• In a two button suit– you button the top button. Do not ever button the bottom one.
• In a one button suit– you button the only button.

The reason this is important is because the fit and drape of the jacket is really based on this waist button. This is why you have probably been told before to button your suit jacket when you are standing. Otherwise, the fit of your jacket simply won’t appear as fine. However when you sit down in a suit jacket of any kind, it is appropriate to undo all of the buttons.

What about if you are attending a wedding and you’re going to be dancing? Interestingly, this answer varies depending on the type of dancing you will be doing. If you are going to be slow dancing, it is appropriate for you to keep your jacket buttoned as indicated above. If you are going to be dancing to fast-paced music, you can keep your jacket unbuttoned entirely. If you are really going to be getting down on the dance floor with your friends, you all may wish to remove your jackets entirely, roll your shirt sleeves up to your elbows, and loosen your tie knots. You should, however, never do this during a nice sit-down dinner. Even if it is hot in the room, do not remove your jacket while dining. It is more appropriate to drink ice water and politely excuse yourself to the restroom to dab off your forehead than it is to dine without your jacket.

Now like most rules, there is an exception with the button rule. If you live in a cold climate and the jacket of your suit is at risk for blowing open while you are outside, by all means, button up all of the buttons on your jacket. There is nothing wrong, in this particular instance, with considering function over form. A fully buttoned up jacket will look better than one that is wildly flapping in the wind. Another exception is with double breasted jackets, which are sort of the odd man out with the button rule. If you have a double breasted jacket, you should button all of the buttons, allowing the jacket to lay correctly. If you need ease of movement in a double breasted jacket, undo only the bottom outside button.