-21.49% is the change from 819 to 643
Calculation steps:
[( 643 - 819 ) ÷ 819] x 100 = -21.49%
Formula
Percentage change = [(643 - 819) / 819] x 100
Subtract the new number by the original number
643 - 819 = -176
-176 ÷ 819 = -0.2148962148962149
-0.2148962148962149 x 100 = -21.49%