Well, the biggest animal rights organisation is saying 80x80x100 cm.
I wouldn't make the depth more than 60 though, because then it gets hard to clean
H = 100 D = 60 and L = 80
I think that would be a quite nice cage for 2 chinchillas.
But bigger would be nice, no question about it
We have a female in a 80x50x70 cm (HxDxL) cage (or something like that), and she is quite fine in that. Actually she tends to get very weird if she gets a very big cage. And it's not because she's mistreated
At one point we had 2 chinnies in that cage, and that worked quete well too. You just need to let them run outsite more often, and for at longer period of time, if you have a relativly small cage
(1 centimeter = 0.393700787 inches - you can get google to figure it out by typing x cm in inches)
The chinchilla comes from the Andes. It's coat's made for cold weather
There are like 5 degrees celcius in my room at winter (i sleep there), and they don't mind at all
It's better if it's a bit cold, than a bit to hot!
I think you should get 2 chinnies.
They are relativly social animals, and like to have a friend to sped time with (they live in colonies in the wild, so they do not live a bunc of chinnies together in the same den