0.31% is the change from 640 to 642
Calculation steps:
[( 642 - 640 ) ÷ 640] x 100 = 0.31%
Formula
Percentage change = [(642 - 640) / 640] x 100
Subtract the new number by the original number
642 - 640 = 2
2 ÷ 640 = 0.003125
0.003125 x 100 = 0.31%
Example