Preparing and setting up your rats’ cage is very important. Your rats will spend a large portion of their lives inside this cage and so you need to make sure it is a safe and fun place to live. Cage Size Each rat should have at least 2 cubic feet of cage space. To make a cage more interesting, choose one with multiple levels and ramps. For senior rats that may have difficulty using ramps or for rats that have balance issues or hind-end degeneration, I suggest a one-level cage