-21.37% is the change from 819 to 644
Calculation steps:
[( 644 - 819 ) ÷ 819] x 100 = -21.37%
Formula
Percentage change = [(644 - 819) / 819] x 100
Subtract the new number by the original number
644 - 819 = -175
-175 ÷ 819 = -0.21367521367521367
-0.21367521367521367 x 100 = -21.37%