You must first decide how much space you have available for your small animal or pet bird. Once you have done this, we recommend looking at a few possible habitats you like and then checking the measurements of those you have selected. For example, if you choose a CritterTrail habitat you could then see the dimensions it provides in the item description. Then with a piece of large paper or a sheet of newspaper, cut out a section the same size as your habitat and place it in the area you will be keeping your new pet. Don’t forget to make sure you also have the right food for your new pet.