One billion dollars in $100 bills laid out would range over 111,287.50 square feet. The standard dimensions of a U.S. currency note are 2.61 inches tall by 6.14 inches long. Ten million $100 dollar bills, laid end to end, would stretch 4,000 miles long.
The answer was found by multiplying the height of the bill, 2.61 inches, by 10 million to arrange the bills end to end. The square footage was found by dividing the length of the chain, 26,100,000 inches, and the length of the bill, 6.14 inches, by 12 and then multiplying the resulting values. The square footage of this chain would be equal to roughly 21 square miles of currency.