The size of a pressure cooker entirely depends on your requirements. If you have a small family you must get a pressure cooker of small capacity like 2-3.5 litre. However, if you have a medium-sized family with more than 3 members you must have a pressure cooker of 5 litres. Also, if you are a part of a big family, you will need a pressure cooker with a capacity of 6-8 litres.