Your rats will spend the majority of their short lives in an enclosure, so it's very important to choose a cage that is suitable for your rats and yourself.
Consider these points -
How many rats do you have?
Where is the cage going and what is the maximum size for that space?
How accessible is the cage for hanging hammocks, changing water, handling rats, etc?
Does it come with shelves or will you need to add shelves?
How will you clean the cage? - large cages should have wheels for easy maneuvering, while small cages can be washed in the shower or outside.
Rats, males most commonly, can become territorial when housed in small cages or with large numbers of rats. For a comfortable living arrangement, ensure that each rat gets at least 2.5 cubic feet of space. You can use our cage calculator to determine how many rats your cage can comfortably hold.
Bar spacing should be a 1/2 inch or smaller - As a general rule, if rats can fit their head in a space, their entire body can follow. Larger adult males can be housed in cages with 1 inch bar spacing.
Shelves are necessary - Rats cannot fly, and therefore they cannot use empty air space. As a way to minimize unused space and provide more climbing options for your rats, add shelves, hammocks, tubes, and more.
Wire levels must be covered - Wire shelves can lead to bumble foot or sprained legs. As a precaution, they should be covered with fleece, cardboard, or tiles.
Rats can escape from plastic cages - Rats love to chew and cages with plastic bases are very easy to escape from. Metal cages are the best option for rats.
Large doors for ease of access - Small doors make it difficult to clean the cage and handle your rats. Larger doors are very convenient when hanging hammocks, changing food, etc.
Large cages should have wheels on the base - The larger the cage is, the more difficult it will be to move. Large cages are heavy and therefore a great feature to have is wheels.