-20% is the change from 810 to 648
Calculation steps:
[( 648 - 810 ) ÷ 810] x 100 = -20%
Formula
Percentage change = [(648 - 810) / 810] x 100
Subtract the new number by the original number
648 - 810 = -162
-162 ÷ 810 = -0.2
-0.2 x 100 = -20%
Example