Calculate how much drink you should buy for the party — both alcoholic and non-alcoholic — based on number of guests and how long the party lasts.
The calculator starts from a common rule of thumb of about one drink per person per hour for those drinking alcohol:
Guests who don't drink alcohol are counted at the same pace in non-alcoholic drinks, while those who do drink alcohol are also counted for half a non-alcoholic drink or water per hour — people often alternate between alcohol and non-alcohol through the evening. For long evenings with lots of dancing and activity, plan a bit extra, since thirst increases.
A common planning rule is about one drink per hour for each guest who drinks alcohol. It's only a starting point — adjust based on what you know about your guests' habits.
It can be worth erring on the generous side, especially for long evenings with lots of dancing and activity, or in hot weather where guests drink more. Unopened bottles can usually be returned or used later.
Not all guests drink alcohol, and even those who do often alternate with non-alcoholic drinks or water through the evening. Good non-alcoholic options make the party better for everyone and help guests stay hydrated.