-85% is the change from 540 to 81
Calculation steps:
[( 81 - 540 ) ÷ 540] x 100 = -85%
Formula
Percentage change = [(81 - 540) / 540] x 100
Subtract the new number by the original number
81 - 540 = -459
-459 ÷ 540 = -0.85
-0.85 x 100 = -85%
Example