You can expect a full-gallon keg to weigh around 72.8 kilograms, while a 50L keg weighs about 58.9 kilograms. A quarter keg is lighter at 39.4 kilograms, and a sixth barrel is more lightweight at 27.2 kilograms.  The lightest of all is the mini keg, which weighs 24.9 kilograms.