26.56% is the change from 64 to 81
Calculation steps:
[( 81 - 64 ) ÷ 64] x 100 = 26.56%
Formula
Percentage change = [(81 - 64) / 64] x 100
Subtract the new number by the original number
81 - 64 = 17
17 ÷ 64 = 0.265625
0.265625 x 100 = 26.56%
Example