-87.46% is the change from 646 to 81
Calculation steps:
[( 81 - 646 ) ÷ 646] x 100 = -87.46%
Formula
Percentage change = [(81 - 646) / 646] x 100
Subtract the new number by the original number
81 - 646 = -565
-565 ÷ 646 = -0.8746130030959752
-0.8746130030959752 x 100 = -87.46%