-50% is the change from 810 to 405
Calculation steps:
[( 405 - 810 ) ÷ 810] x 100 = -50%
Formula
Percentage change = [(405 - 810) / 810] x 100
Subtract the new number by the original number
405 - 810 = -405
-405 ÷ 810 = -0.5
-0.5 x 100 = -50%
Example