The number of beers in a keg depends on the size of the keg and the serving size (glass of beer) of each beer. In most cases, a standard beer serving is considered to be 12 ounces (355 milliliters), especially in the United States of América. The most common keg size in the U.S. is the half-barrel keg, which holds 15.5 gallons of beers. When converted, that equals around 1,984 ounces. If each beer is 12 ounces, a half-barrel keg contains nearly 165 twelve-ounce beers.

There are other keg sizes. A quarter-barrel keg (also called a pony keg) holds 7.75 gallons, which equates to around 82 twelve-ounce beers. A sixth-barrel keg (often used by craft breweries and in home kegerators) holds 5.16 gallons, or around 55 twelve-ounce beers. For homebrewers, a Cornelius keg or “Corny keg” holds five gallons, providing about 53 twelve-ounce servings.

In Europe, kegs are often measured in liters. A standard European or UK keg is 50 liters, which equals nearly 169 standard U.S. beers or 140 UK pints, since a UK pint is 20 ounces. Smaller 30-liter and 20-liter kegs yield proportionally fewer servings.

It's important to note that foam loss, over-pours, and spillage can marginally reduce the actual number of full servings you get from a keg, especially in fast-paced environments like parties or bars. In addition, the number of servings will differ if beer is poured into larger pint glasses instead of 12-ounce bottles or cans.

So, while the exact number can vary slightly depending on serving size and usage conditions, you can expect a full-size keg to provide approximately 160 to 170 standard beers, making it a popular and cost-effective option for events and gatherings.

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