386.36% is the change from 66 to 321
Calculation steps:
[( 321 - 66 ) ÷ 66] x 100 = 386.36%
Formula
Percentage change = [(321 - 66) / 66] x 100
Subtract the new number by the original number
321 - 66 = 255
255 ÷ 66 = 3.8636363636363638
3.8636363636363638 x 100 = 386.36%