-21.03% is the change from 813 to 642
Calculation steps:
[( 642 - 813 ) ÷ 813] x 100 = -21.03%
Formula
Percentage change = [(642 - 813) / 813] x 100
Subtract the new number by the original number
642 - 813 = -171
-171 ÷ 813 = -0.21033210332103322
-0.21033210332103322 x 100 = -21.03%