Formula
Drinks per drinking guest are the first-hour rate times the first hour, or the fraction of an hour if the event is shorter, plus the later rate times every hour after the first. Total drinks are guests times the drinking share times that rate times one plus the cushion. Beer, wine, and liquor split that total. A 750 mL bottle is 25.36 fl oz. Wine pours per bottle are that volume divided by the pour, rounded down. Shots are the same. Containers round up.
drinks = guests × drinkers × (first hour + later hours) × (1 + cushion)
750 mL = 25.36 fl oz → 5 pours of 5 fl oz, 16 shots of 1.5 fl oz
Light, average, and heavy only change the two rates you can also type: 1 and 0.5, 2 and 1, or 3 and 1.5. Those are labelled assumptions. A crowd, a long meal, or a short cocktail hour is a reason to edit the hours, not a different formula. Ice and mixers are left out. No price on this page is a market price.
Worked examples
100 guests, everyone drinks, 5 hours, no cushion. 600 drinks. Beer 10 cases, wine 48 bottles, liquor 8 bottles of 750 mL.
Same list with 10 percent cushion. 660 drinks, 11 cases, 53 wine bottles, 9 liquor bottles. At 80 percent drinking and no cushion, 480 drinks. A half-hour event for 50 guests is 50 drinks. A toast for 100 at 6 glasses a bottle is 17 bottles. 120 shots in 1.75 L bottles is 4 bottles.
Reference
1 L is 33.81 fl oz, 22 shots of 1.5 fl oz. 1.75 L is 59.18 fl oz, 39 shots.
Questions
How much alcohol do I need for 100 guests?
At the default planning rates, 2 drinks in the first hour and 1 each hour after, five hours is 6 drinks a person. If everyone drinks and there is no cushion, that is 600 drinks: 10 cases of beer, 48 bottles of wine, and 8 bottles of 750 mL liquor at a 40/40/20 mix.
How many drinks per person at a wedding?
The opening assumption is 2 in the first hour and 1 per hour after that. It is a typical planning assumption, not a rule and not advice about how much anyone should drink.
How many bottles of wine per guest?
In the 100-guest example, 240 wine drinks and 5 pours per 750 mL bottle is 48 bottles, under half a bottle per guest. Change the mix and the hours and the count changes.
How many bottles are in a case?
Beer is counted at 24 bottles or cans. Wine is counted at 12 bottles of 750 mL. Both are editable.
How much champagne for a toast?
At 6 glasses per bottle, 100 guests is 17 bottles. Six is the default glasses per bottle, and you can change it.
Should I over-order?
A planning cushion, defaulting to 0 and editable, multiplies the drink count. Ten percent on the example is 660 drinks. Leftovers and a short pour are a hosting choice.
Open bar or a limited bar?
An open bar is every drink in the mix. A limited bar is a shorter list you build by changing the percentages. This page does not price either one.
Sources
- National Institute on Alcohol Abuse and Alcoholism, “What is a standard drink.” In the United States one standard drink is about 14 grams of alcohol: 12 fl oz of regular beer at about 5% ABV, 5 fl oz of table wine at about 12%, or 1.5 fl oz of 80-proof spirits at 40% ABV. NIAAA notes that customary pours vary.
- The first-hour and later-hour rates are a typical planning assumption on this page. No caterer schedule was copied.
- 750 mL = 25.36 fl oz, 1 L = 33.81 fl oz, 1.75 L = 59.18 fl oz. Servings per bottle round down.