See, there's two ways you can figure out how much beer is in a keg. You can measure the outside of it, figure out how much each component weighs, do a lot of fancy math, and probably come out with a really precise answer. Or, you can do what they did:

How much is inside a keg? Any college sophomore can tell you it is 15 gallons, but how many servings is that, and how many gallons should you plan for each guest?

On Saturday night, we decided to find out.

Back in college we used to get a pony every weekend. It was a lot cheaper than buying cans and, since you could drink whatever amount you liked instead of a fixed 12 oz, it lasted longer. We kept each one of the plastic caps that covered the tap ring, and enjoyed watching freshmen goggle at the wall of circles we built up over a semester.

Good times, good times...