-97.44% is the change from 820 to 21
Calculation steps:
[( 21 - 820 ) ÷ 820] x 100 = -97.44%
Formula
Percentage change = [(21 - 820) / 820] x 100
Subtract the new number by the original number
21 - 820 = -799
-799 ÷ 820 = -0.974390243902439
-0.974390243902439 x 100 = -97.44%