A stack of 100 dollar bills is approximately 0.43 inches thick. Every paper bill in the United States is 0.0043 inches thick, so 100 bills together is 0.43 inches.
Each bill is also 2.61 inches by 6.41 inches, making the square area of a bill 16.7301 square inches. Bills have been this dimension since 1929; before that time, bills were 3.125 inches wide and 7.4218 inches long.
Most $100 bills are in circulation longer than lower-denomination bills, as they are handled less. For instance, most $100 bills last about nine years, while a $1 only stays in circulation about a year and a half.