-95.16% is the change from 640 to 31
Calculation steps:
[( 31 - 640 ) ÷ 640] x 100 = -95.16%
Formula
Percentage change = [(31 - 640) / 640] x 100
Subtract the new number by the original number
31 - 640 = -609
-609 ÷ 640 = -0.9515625
-0.9515625 x 100 = -95.16%