A good rule of thumb is that your guests will enjoy 1½ drinks per hour, per guest.
If you have 100 guests for a 4 hour celebration, your formula will look like this:
Serving size: 5 ounces
750 ml = 5 servings
1.5 liter = 10 servings
Serving size: 3 ounces
750 ml = 8 servings
Serving size: 1 ounce
750 ml = 25 servings
1 liter = 33 servings
1.75 liter = 59 servings
Serving size: 12 ounces
½ barrel keg = 120 servings
¼ barrel keg = 60 servings*
TIP: BOTTLES – for upscale party; CANS – for picnics or pool and lake parties.