We get asked this question all the time. How much alcohol do I need to buy for my party? Figuring out how many bottles of wine you need for a small dinner party might be easy, but what about planning for a large event like a wedding reception or a family reunion? Here are some guidelines for calculating how much wine, beer, and liquor you’ll need for a party, no matter the size.
First, figure out how many drinks you’ll need for the duration of the party. As a general rule, assume guests will have two drinks during the first hour of the party, and one drink every hour after that.
Next, figure out how you want to divide those drinks among wine, beer and liquor, depending on the crowd you’re serving. Or to make it simple, just allocate a third of the total number of drinks to each type.
Wine: A regular size bottle is 750-ml bottle of wine contains about 5 servings, so divide the number of wine drinks by 5 to come up with the number of bottles you’ll need. For Champagne or sparkling wine, a bottle will fill about 6 flutes.
Beer: For large parties, a keg often makes the most sense. In general U.S. half-barrel kegs are 15.5 gallons and quarter-barrels contain 7.75 gallons, which, if you are using 10-ounce cups, this equals about 100 to 200 servings depending on your keg size.
Liquor: Don’t get crazy and buy every mixer under the sun. Stick with basics such as Soda Water, Tonic, a Juice & a Soda. Mixed drinks have a 1.5-ounce (45 ml) serving of liquor per drink, so a 750-ml bottle will make about 16 drinks. To figure out how many bottles you need, just divide the number of liquor drinks needed by 16. Like the mixers create a modified bar picking 3 to 5 main liquor choices. i.e.: vodka, gin, Whiskey. Alternately you can add Rum or Tequila.
To estimate the amount of mixers needed, figure about 1 quart (1 liter) of tonic water, soda water, or juice for every 3 guests.
A great way to not be shocked by the overall alcohol cost may be to start buying alcohol at the store piece by piece in the months leading up to the big day. The trick is just not to drink it!
Check out this basic guide from http://apracticalwedding.com/2014/06/how-to-buy-alcohol-for-your-wedding/