-36.72% is the change from 128 to 81
Calculation steps:
[( 81 - 128 ) ÷ 128] x 100 = -36.72%
Formula
Percentage change = [(81 - 128) / 128] x 100
Subtract the new number by the original number
81 - 128 = -47
-47 ÷ 128 = -0.3671875
-0.3671875 x 100 = -36.72%