How Many Diagonals does An Octagon have?

There are 20 diagonals in an octagon. There is a real simple formula for figuring out diagonals for any polygon. The formula is (n/2) x (n-3). N would be the number of sides the polygon has. So for an octagon it figures out as, (8/2) x (8-3). Which would then be 4 x 5 which equals 20.