How much area does a 20 oz. cup on a sprayer cover?

I'm looking at different sprayers and I was just wondering how much area will a 20 oz. cup cover. Will it cover a whole car for each coat? How much will a 4 oz. cup cover?

depends on who is spraying and how thick they are layin it down

Wow. thanx for all the help guys. I was just looking for an estimated answer but everyone was just so descriptive!!!

it took me 6 cans of 15oz rustoleum to cover my truck.........