-96.82% is the change from 661 to 21
Calculation steps:
[( 21 - 661 ) ÷ 661] x 100 = -96.82%
Formula
Percentage change = [(21 - 661) / 661] x 100
Subtract the new number by the original number
21 - 661 = -640
-640 ÷ 661 = -0.9682299546142209
-0.9682299546142209 x 100 = -96.82%