How much space do I need for more than one cat? Written by Russel in A How much space do I need for more than one cat? Measure the length and width of the space in square feet. Multiply the two numbers then divide them by 18. The answer you get represents the number of cats that will fit in that space. Russel A pet owner who loves to share useful facts and information about animals. For now, I write mostly about dogs and cats.