How big are finches? are they smaller then a parakeet or bigger?

i found a cage for my parakeet but hes at school right now but im going to bring him home and i need a cage....i found one but it says its for finches not parakeets. and in the pic it lookes like 8 finches can fit in there and still have room. should i get the cage? its at petco.com and its a boxish white cage.