-81% is the change from 100 to 19
Calculation steps:
[( 19 - 100 ) ÷ 100] x 100 = -81%
Formula
Percentage change = [(19 - 100) / 100] x 100
Subtract the new number by the original number
19 - 100 = -81
-81 ÷ 100 = -0.81
-0.81 x 100 = -81%
Example