-63.22% is the change from 870 to 320
Calculation steps:
[( 320 - 870 ) ÷ 870] x 100 = -63.22%
Formula
Percentage change = [(320 - 870) / 870] x 100
Subtract the new number by the original number
320 - 870 = -550
-550 ÷ 870 = -0.632183908045977
-0.632183908045977 x 100 = -63.22%