-84% is the change from 800 to 128
Calculation steps:
[( 128 - 800 ) ÷ 800] x 100 = -84%
Formula
Percentage change = [(128 - 800) / 800] x 100
Subtract the new number by the original number
128 - 800 = -672
-672 ÷ 800 = -0.84
-0.84 x 100 = -84%
Example