Ideally the cage should be placed in a room of constant temperature, away from draughts and out of direct sunlight and any other pets that may be a threat to the rat/s.  It should also be kept in a relatively quiet area of the house.

Minimum Cage Sizes

Ideally, a fully grown rat should get about 2 cubic foot in a cage.  However, this does not take into account any shelves,etc in the cage so, really, try and give the rat at least 2 square foot of space, including base of cage and shelves, and try to make sure each level of shelves has at least 12 inches in between.  General rule of thumb would be to use this as a rough guide and then go for something slightly bigger - the more space a rat has, the happier it will be.Why not try our Rat Cage Calculator?  It doesn't take volume of cages into account, but rather shelf room and floor space, which might be able to give you a pretty close estimate of how many rats your cage will hold.

Cage Types

Ordinary barred/wire cages, like ferret and rabbit cages, are ideal for rats as long as the bars aren't spaced too far apart.  They allow for adequate ventilation, a good thing as a build up of ammonia is bad for a rat's respiratory system.  Stay away from galvanized steel cages as they contain zinc, which can poison rats if chewed or licked.  They can also develop foot calluses on wire floor cages, which can become infected and painful.  In addition their legs may also get caught between the wires.  To prevent this the cage floor could be lined with glass or Plexiglas.  Wood is not ideal as it can soak up urine and is difficult to disinfect and rats are likely to chew the wood.  Bar spacing on these kind of cages can cause some problems.  Many ferret and rabbit cages have quite wide spaced bars and young rats, or rats small for their age, could easily squeeze out and escape, or get themselves stuck.  One way of getting around this is to cover the outside of the cage in tight-fitted pet wire, but this can be quite a time consuming job.
Two (or more) level wire cages are an even bigger bonus, as they can provide stimulation and entertainment for rats in the form of ladders and ramps, hanging accessories (such as hammocks) and more.  Rats love to climb and giving them the extra levels will give them that much more enjoyment.
Hamster cages are really too small, but could mage great hospital cages, for sick or poorly rats who won't be moving around much.  They can also double for new mums, as the bar spacing would be too small for any tiny members of the new litter to escape through.
Aquariums can make good rat houses, as they are draught proof and normally reasonably priced.   Make sure any aquarium you buy has a lockable, ventilates, cover to prevent any escapees.  The aquarium should also be of suitable size, and not the smallest they had in the shop, just because it was cheap.  Some people say due to the lack of levels, etc, that aquariums aren't as suited to rats as barred cages, but a good sized aquarium can still be fitted with climbable items and other interesting novelties to keep rats entertained.  They can be cumbersome and awkward to clean however, and need cleaned out regularly to prevent build up of ammonia.
Home made cages are another way to go.  These can be done by converting old cupboards and shelves, or by starting from scratch.  It can be a long process making your own cage, but sometimes the results are worth it, as you can design it exactly to fit the amount of rats you have, as well as plan well for adding levels, climbable areas, etc.  Just make sure that, if using wood, you protect it in some way, as it will soak up urine at a rapid rate and you'll probably find you'll never get it cleaned properly.

Where to purchase cages

Most pet stores nowadays do suitable cages for rats.  If you shop around you should find one suited to your needs.  Be warned, however, that big cages, like rabbit and ferret, are much more expensive than hamster cages, so be prepared to pay extra.  One of our cages cost us nearly £200, but it has been well worth the payment.
Some online places to buy cages are: