150% is the change from 256 to 640
Calculation steps:
[( 640 - 256 ) ÷ 256] x 100 = 150%
Formula
Percentage change = [(640 - 256) / 256] x 100
Subtract the new number by the original number
640 - 256 = 384
384 ÷ 256 = 1.5
1.5 x 100 = 150%
Example