-21.44% is the change from 821 to 645
Calculation steps:
[( 645 - 821 ) ÷ 821] x 100 = -21.44%
Formula
Percentage change = [(645 - 821) / 821] x 100
Subtract the new number by the original number
645 - 821 = -176
-176 ÷ 821 = -0.2143727161997564
-0.2143727161997564 x 100 = -21.44%