hi amy,
found this for you.
Quote: Q: I am having 10 guests at my party. How much liquor should I purchase?
A: You can assume that 10 guests will consume about 4 to 5 drinks for the evening. If you are just serving hard alcohol, that's approximately 20 shots. (Based on 1.5 oz. per shot - - 2 per person). A bottle of wine usually yields about 5 cocktails. If you buy beer, consider purchasing 6-packs or bottles.
Quote: Party Food Planning:
Beverage Calculator
Include beverages in your party food planning. The amount of punch or number of cocktails or beers a guest will drink varies. Allow for the length of the party, the strength of the beverage, the day of the week, the rowdiness of the crowd, or lack thereof, and adjust your figure accordingly. The rules-of-thumb are:
Punch: Figure 10 people to the gallon-- pretty good mileage. That's a conservative estimate, assuming your guests will drink about three 4-ounce servings during the party.
Cocktails: Figure that your guests will consume 2 drinks per person per hour for the first 2 hours and 1 drink per person per hour after that.
What to stock for your cocktail party:
As for liquor, purchase at least one 750-mil bottle (standard size) each of scotch, rum, bourbon, tequila, vodka and gin if that is practical for you. Each bottle contains about 16 1 1/2-ounce shots. (The same size bottle of wine or champagne contains 6 4-ounce servings. One 12-ounce beer is considered one serving.)
Stock mixers such as club soda, lime juice and other fruit juices, tonic water, and non-alcoholic beer in small bottles so that unopened containers may be used in future.
Stock 1 pound of ice per person if the drinks need to be iced. More will be needed for an outdoor, warm-weather party, or if the party lasts a long time. Only about half that though, 1/2 pound of ice per person, is needed if the beverages are pre-chilled or the party is of short duration.
Figure about 4 cocktail napkins (or 2 linen napkins) per person per hour, less if your guests will be using small cocktail plates for food.
Stock enough glasses that your guests can trade a dirty one for a clean one at least once, maybe more.