-19.12% is the change from 821 to 664
Calculation steps:
[( 664 - 821 ) ÷ 821] x 100 = -19.12%
Formula
Percentage change = [(664 - 821) / 821] x 100
Subtract the new number by the original number
664 - 821 = -157
-157 ÷ 821 = -0.19123020706455543
-0.19123020706455543 x 100 = -19.12%