57.58% is the change from 521 to 821
Calculation steps:
[( 821 - 521 ) ÷ 521] x 100 = 57.58%
Formula
Percentage change = [(821 - 521) / 521] x 100
Subtract the new number by the original number
821 - 521 = 300
300 ÷ 521 = 0.5758157389635317
0.5758157389635317 x 100 = 57.58%