100% is the change from 250 to 500
Calculation steps:
[( 500 - 250 ) ÷ 250] x 100 = 100%
Formula
Percentage change = [(500 - 250) / 250] x 100
Subtract the new number by the original number
500 - 250 = 250
250 ÷ 250 = 1
1 x 100 = 100%
Example