-90.13% is the change from 821 to 81
Calculation steps:
[( 81 - 821 ) ÷ 821] x 100 = -90.13%
Formula
Percentage change = [(81 - 821) / 821] x 100
Subtract the new number by the original number
81 - 821 = -740
-740 ÷ 821 = -0.9013398294762485
-0.9013398294762485 x 100 = -90.13%