100% is the change from 64 to 128
Calculation steps:
[( 128 - 64 ) ÷ 64] x 100 = 100%
Formula
Percentage change = [(128 - 64) / 64] x 100
Subtract the new number by the original number
128 - 64 = 64
64 ÷ 64 = 1
1 x 100 = 100%
Example