-18.39% is the change from 821 to 670
Calculation steps:
[( 670 - 821 ) ÷ 821] x 100 = -18.39%
Formula
Percentage change = [(670 - 821) / 821] x 100
Subtract the new number by the original number
670 - 821 = -151
-151 ÷ 821 = -0.18392204628501826
-0.18392204628501826 x 100 = -18.39%