-97.47% is the change from 830 to 21
Calculation steps:
[( 21 - 830 ) ÷ 830] x 100 = -97.47%
Formula
Percentage change = [(21 - 830) / 830] x 100
Subtract the new number by the original number
21 - 830 = -809
-809 ÷ 830 = -0.9746987951807229
-0.9746987951807229 x 100 = -97.47%