-49.69% is the change from 638 to 321
Calculation steps:
[( 321 - 638 ) ÷ 638] x 100 = -49.69%
Formula
Percentage change = [(321 - 638) / 638] x 100
Subtract the new number by the original number
321 - 638 = -317
-317 ÷ 638 = -0.49686520376175547
-0.49686520376175547 x 100 = -49.69%