How many cups of beer per keg?

What people typically call a "keg" in the US is actually a 1/2-barrel keg." A barrel of beer is 31 gallons, so a keg would have 15 1/2 US gallons of beer, or 1984 ounces.

If you are using twelve ounce cups, that equals out to about 165 cups. If you are with real beer drinkers, you will want to pour a pint (16 ounces). You'll get 124 pints.

If you are talking about actual 8-ounce cups, there would be 248 cups.