A larger drum for the same rated capacity gives laundry more room to move, which tends to help rinsing and reduce creasing. Manufacturers do not all publish it, and the figure is not on the energy label.
As a rough guide, UK front loaders of 7 to 9 kg have drums of about 55 to 65 litres, and 10 to 12 kg machines about 70 to 80 litres. Where the drum volume is missing, the depth of the appliance is the best proxy: slim machines of 450 mm or less have smaller drums than full-depth machines at 600 mm or more.
Frequently asked questions
What does drum volume mean on a washing machine?
The drum volume is the internal capacity of the drum in litres. It is a physical size, unlike the rated capacity, which is a declared weight of laundry.