-97.42% is the change from 815 to 21
Calculation steps:
[( 21 - 815 ) ÷ 815] x 100 = -97.42%
Formula
Percentage change = [(21 - 815) / 815] x 100
Subtract the new number by the original number
21 - 815 = -794
-794 ÷ 815 = -0.9742331288343559
-0.9742331288343559 x 100 = -97.42%