# of Cavies--Minimum--Preferred
Two---------7.5 sq. ft.--10 sq. ft.
Three--------10.5 sq. ft.-13 sq. ft.
Four---------13 sq. ft.---more is better
With more than five of us, you'll have to get a very large cage. For any number of guinea pigs, we recommend Guinea Pig Cages Store as a good site for buying cages. They also have a number of accessories. I personally know the importance of having a nice, large cage (or island in our case); I used to run around the island, popcorning (jumping) and having fun. Please make sure your guinea pig gets the chance to do that.
~Celery