The standard American half-barrel beer keg holds 15.5 gallons. This is equal to 165 12-ounce servings, or 124 16-ounce servings. The American half-barrel keg is 23.3 inches tall with a diameter of 16.1 inches. It weighs 160.5 pounds when full, but only 29.7 pounds when empty.
There are other keg sizes available that hold various amounts. Beginning with the smallest, a mini keg holds merely 1 1/3 gallons. A soda keg can hold five gallons. Coming in slightly larger, a sixth barrel contains 5 1/4 gallons. A one-fourth keg holds 7 3/4 gallons. Lastly, a European keg holds 13.2 gallons.