I have a larger sized 4-door sedan. About half a roll of Raammat did one layer over my entire trunk, and I used the rest to do about 2 heavily overlapped layers on each front door (we'll call it 3 layers //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif ) and one layer on my front floorboard.
I'd start with 1 roll of Raammat as suggested by Jim and see how far it gets ya.
Excellent deadener and Rick, the owner, is an awesome guy to deal with.