Surely, the bigger the cage, the better for your pet. However, if one rat needs at least 25 x 15 x 20 inches, for two and more rats you should twice enlarge these dimensions. Such cages like 2-Story MidWest Deluxe Critter Nation #162, Prevue Hendryx Black Feisty Ferret Cage, Kaytee Ferret Home Plus, Prevue Hendryx 495 Earthtone Dusted Rose Cage offer large space and several levels to accomadate two and even more rodents with maximum comfort.