Washing machines have different drum sizes. These are measured in kg, and tell you the maximum weight of dry washing that you can put in. The bigger the number, the larger the drum and the more washing that you can do in one load. Larger drum sizes are also useful if you want to wash more generously sized items, such as duvets. Typically, most households will find that a minimum of a 6kg drum will do for weekly washing; go for 8kg or larger if you have a lot of washing.