Measure with the next empty milk carton generated in your household. 5 litres is pretty small - only just holds a smallish chicken. Does chicken pieces pretty good though. Living alone, I don’t need anything much bigger than that. When the boyos and my late partner were in the house, I used it for like the meat part of the meal only, and did the rest on the stovetop or in the oven. The beautiful thing about a slow cooker is that it’s almost impossible to burn anything in it.