for 3 chins
At least 30"x30"x60". The more the better always. I actually have one chinchilla and I built his cage and its a little bigger than that for just him. It was 24x24x36 but I added on-the old is the new top and the new bottom is about 36"x36"x36". Once I added on, he was soooo much happier. And he has a 12" ledge now for when he's out of his cage that he sits on after doing sprints. His cage is part of the obstacle course, lol. He no longer climbs all the way to the top, though, which I'm honestly happy about. I have to stand on his one door (the cage is very sturdy) to clean his top shelf, lol! I'm only 5' 2". They love space for climbing, jumping, doing laps, etc. He's a happy, healthy little guy!