Question: how much dirt to cover 1 acre?
Answer: According to Wikipedia, acre is 43,560 square feet. So, if you dig 1 foot deep over an acre, you get 43,560 cubic feet of dirt. If you dig 5 feet deep, then you have 5 times this amount of dirt. If you dig 5 feet of dirt out of 50 acres, then you have 50 times as much dirt as if you did that over 1 acre.