What button do you leave open on a tuxedo?

The rule of thumb for not only a tuxedo but any men's suit jacket, dress/dinner jacket or sport coat is that you never, ever, ever, button the bottom button.

A tuxedo jacket is commonly constructed with two button or a single button and you may also run across a three button tuxedo jacket which is slightly less popular and also, now a days; the double breasted tux is back in style. Now let me explain which button to leave open for each style of jacket:

1. Two button tuxedo jacket: Leave the bottom button open

2. Three button tuxedo jacket: Leave the bottom button open. If you're wearing a vest under your jacket, then you may also leave the top button open but that's not mandatory, just personal preference.

3. Single button tuxedo jacket: Only unbutton your jacket when you're seated otherwise, keep the single button, buttoned at all times.

4. Double Breasted tuxedo jacket: unbutton the bottom button. Now having said that, although it's ill-advised; a double breasted jacket is the only jacket where if you absolutely wish to do so, you can button the bottom button without making it appear as though you're making a big style mistake.

In other Words; it's not as bad as buttoning the bottom button of a two or three button jacket.