Despite numerous experimental studies, there is no consensus on minimal or optimal cage space for small rodents.  There are several rat cage calculators available on the internet, but how the space is used and the amount of outside time the rats will receive per day, plays an important role.

Instead of calculating the cage space volume, plan the cage according to the following;

The cage area should be three dimensional, comprised of the floor area as well as vertical climbing space.  Rats should be able to turn freely, run or walk for short distances, stand on their hind legs and stretch.   

A large cage is desirable but an enriched environment allowing the rats to express natural behaviour is of an even higher value. You need enough space for accessories, dividing the cage in the following areas:

• An area for sleeping, nesting or hiding away, especially during the day. Many rats are very sensitive to light and need a darker area where they can sleep.  If possible, provide more than one sleeping area to allow a rat to get away from the other rats if needed.

• An area to eat or forage.  Either provide a bowl or scatter feed food.  Scatter feeding is advised to promote natural behaviour. 

• Enough space for manipulating, carrying and hoarding objects and food.  This includes nest building.  Supply interesting new objects to the cage from time to time.  This need not be expensive.  A cardboard box, hay or a few mulberry branches will keep your rats more than happy.

• An area to exercise, explore and engage in social activities like running, climbing, digging or burrowing. If your cages don’t allow this, you will need to give your rats time outside the cage to exercise. If you don’t have a dedicated rat room, a bathroom, table top or playpen can work well.

• An area to defecate like a litter box.  This is one of the most important must haves for a rattery.  Rats using a litterbox will not only keep the cages cleaner for longer and easier to clean, it will also help with ammonia control which is not only smelly but also harmful to the rats’ sensitive respiratory systems. YouTube: The litterbox and pee stone

• Allow space for accessories that can be chewed like cardboard boxes or rolls, wooden chew toys or hay.  Rats are rodents.  It is part of their normal behaviour.