A standard bottle of wine (750ml) provides five 5oz glasses of wine.
For a sit-down dinner party, plan on half a bottle of wine
per guest. Then, buy an extra bottle or two, just in case the festivities go on
longer than anticipated, or guests want a glass of wine before or after dinner.
For a cocktail party with a caterer or waiter, plan on
one-third to one-half bottle of wine per person, per two-hour period. If
you’re also serving hard liquor and your guests are divided in their
preferences, go for the one third amount..