Our awesome alcohol calculator will determine your needs! It determines how many bottles of wine, beer, and liquor you will need based on your specific guests.Read on for how to break that up for beer, wine and cocktails! Wondering how much alcohol you will need for your next event? Use our Alcohol and Bar Calculator to accurately estimate the amount of alcohol and supplies needed for your event. Do you need to hire a bartender in Washington? We provide bartending services from weddings and parties to events and mobile bartending. Here are some tried and true recommendations for calculating the drink servings that you will need at your party based on your guest count. Here's a basic formula: Total Alcohol Needed = (Average Drinks per Guest) × (Number of Guests) × (Duration of Event in hours) × (Percentage of Alcohol Content) Event and Wedding use this formula it will tell you how much alcohol you need to buy for your next upcoming Event!