-96.75% is the change from 646 to 21
Calculation steps:
[( 21 - 646 ) ÷ 646] x 100 = -96.75%
Formula
Percentage change = [(21 - 646) / 646] x 100
Subtract the new number by the original number
21 - 646 = -625
-625 ÷ 646 = -0.9674922600619195
-0.9674922600619195 x 100 = -96.75%