320% is the change from 100 to 420
Calculation steps:
[( 420 - 100 ) ÷ 100] x 100 = 320%
Formula
Percentage change = [(420 - 100) / 100] x 100
Subtract the new number by the original number
420 - 100 = 320
320 ÷ 100 = 3.2
3.2 x 100 = 320%
Example