How many bottles of wine should I buy for a dinner party?
For a dinner party, it's advisable to buy as many bottles as there are guests, since almost one bottle per person is consumed during a long evening.
An accurate calculation depends on several factors: the bottle's volume, the number of guests, the party's duration, and the average number of glasses consumed. Rachel Davis of ABC Fine Wine & Spirits notes that, on average, guests have two glasses in the first hour and one more for each subsequent hour.
With a four-hour dinner, Davis's rule suggests that each guest should expect to drink at least four glasses. Since a 750ml bottle yields five standard 150ml glasses, this equates to almost a whole bottle per person. Davis notes an exception with champagne: due to the smaller glass size, six servings per bottle should be expected.
The guest list matters, too. Bon Appétit calculated how many glasses guests might consume based on their preferences: occasional drinkers might only have one, while wine connoisseurs familiar with America's most underrated wine regions could order at least several.
The alcohol percentage also affects the recommended serving size: the higher the percentage, the smaller the glass should be. Many styles with over 20% alcohol, such as port and vermouth, are often used as digestifs after a meal.
In practice, serving wine is a rough estimate, and the variation increases when guests pour for themselves. Some prefer small portions to aerate the wine and sample several bottles, while others pour 177 or 207 ml so they don't have to get up to pour more. When in doubt, it's best to buy an extra bottle.