Keg Sizes: complete chart

Understanding the standard keg sizes

Every US keg size is a fraction of a barrel, and a barrel is a legacy of English brewing law: 31 US gallons. A half barrel holds 15.5 gallons, a quarter barrel holds 7.75, and a sixth barrel holds one-third of a half — 5.16 gallons. The terms "pony keg" (quarter barrel) and "sixtel" (sixth barrel) are nicknames that crept in because the full names are awkward, but the math never changes: one gallon of beer is 128 fluid ounces.

The Cornelius keg is the odd one out. Built from surplus soda-industry tanks in the 1950s and 1960s, the "Corny" holds exactly 5 gallons and became the workhorse of homebrewing because it is reusable, easy to clean, and fits almost any kegerator. It is not a true barrel fraction, but it is the most common keg in American homes after the sixtel.

Knowing the sizes matters for more than parties. If you buy beer by the keg for a home tap, the size you choose decides whether you are refreshing the keg every weekend or drinking from a tap that has gone stale. A sixtel is right for a light drinker; a half barrel makes sense for a house that hosts. And if you are tracking how much a habit really costs, the cost calculator will do the same math for cigarettes that kegs are doing here for beer.

Kegs vs cases: the beer math

A US case is 24 twelve-ounce bottles or cans — 288 ounces of beer. Divide any keg's total ounces by 288 and you get its case-equivalent: a half barrel (1,984 oz) is roughly 6.9 cases, a quarter barrel is 3.4 cases, a sixtel is 2.3 cases, and a Corny keg is about 2.2 cases. Kegs almost always win on price per beer because you are not paying for individual bottles, cartons, and shelf space — but you are also committing to finishing the whole keg before it goes flat.

The case comparison changes the buying decision. If you entertain once a month, the 2.3 cases in a sixtel is a comfortable commitment, and its ~55 beers at $1.09–$1.64 each still beat retail. If you drink a couple of beers a night at home, the keg economics turn upside down: a sealed, refrigerated keg under CO2 stays fresh for roughly 45–90 days, but an unpressurized partial keg starts losing carbonation within about a day and will stale in days. A small kegerator changes all of that — and if you are comparing costs, the party drink calculator does the same math for cocktails that kegs do for beer.

Beyond the US sizes: 50L European kegs and mini kegs

The US barrel system is not the only one. Imported European lagers often arrive in a 50L keg (about 13.2 US gallons), which holds roughly 140 twelve-ounce beers — noticeably more than a sixtel and a bit less than a half barrel. European kegs use a different coupler connection than domestic ones, so they need the right tap fitting; import-friendly retailers will tell you which coupler a keg needs before you buy.

On the home side, mini kegs fill the gap below the Corny. A 5L mini keg (1.3 gallons) pours about 14 twelve-ounce beers — the size of a large growler with a tap — and costs $10–$20 for popular brands at grocery and liquor stores. They use CO2 cartridges or hand pumps, so they need no kegerator, but they drink fastest: once opened, a 5L keg should be finished within 24–48 hours or it goes flat.

The rule for picking any size is simple: estimate your guests, add a buffer for foam, and choose the smallest keg that covers the night. A half barrel that goes stale in week two costs more than a sixtel you run out of at hour four. And when beer is the occasion, the how many beers in a keg page has the full party-planning math.