How Big Should A Rabbit Cage Be?

Your rabbit's cage should be at least four times the size of the rabbit. It must have a floor that is not wire mesh, as this will hurt the rabbits paw pads. In one corner you should put a litter box, and this will reduce the amount of times you have to clean the whole cage.
Rabbit's are crepuscular, which means they are active during the dawn and twilight hours. You must let your rabbit out to play during the morning and evening hours otherwise it will feel cooped up. Also, don't let it out unsupervised if it is untrained.
When let out to play, make sure there are no cords they can chew on, or things they can eat (like toxins). Provide them with plenty of toys and they will be very busy playing with them.

At least 4 times the size of the rabbit but the bigger the better.

It should be big enough for the rabbit to be able to run around.But like cinnamon said they spend most of there life outside of the cage.

Generally when one has rabbits as pets, their time gets divided between running free in the house and being in their cage. Hence if your rabbit is spending more than half its life in the cage, you should do your best to ensure that it is comfortable enough. There are a variety of rabbit cages available in the market, however many of them do not make for suitable enough homes for your pet. Most of the ones available are way too small; others may come with wired floors, which are not really comfortable for your little bunny rabbit.

Deciding how big a rabbit cage should be is simple. The bigger the cage is, the better it is for your rabbit. However the minimum requirement for a rabbit cage size is that it should be four times the size of your rabbit. Depending on this, you can get any cage which meets your other practical requirements.

Um as big as you!!!!