-21.14% is the change from 809 to 638
Calculation steps:
[( 638 - 809 ) ÷ 809] x 100 = -21.14%
Formula
Percentage change = [(638 - 809) / 809] x 100
Subtract the new number by the original number
638 - 809 = -171
-171 ÷ 809 = -0.21137206427688504
-0.21137206427688504 x 100 = -21.14%