-50.61% is the change from 820 to 405
Calculation steps:
[( 405 - 820 ) ÷ 820] x 100 = -50.61%
Formula
Percentage change = [(405 - 820) / 820] x 100
Subtract the new number by the original number
405 - 820 = -415
-415 ÷ 820 = -0.5060975609756098
-0.5060975609756098 x 100 = -50.61%