20.85% is the change from 820 to 991
Calculation steps:
[( 991 - 820 ) ÷ 820] x 100 = 20.85%
Formula
Percentage change = [(991 - 820) / 820] x 100
Subtract the new number by the original number
991 - 820 = 171
171 ÷ 820 = 0.20853658536585365
0.20853658536585365 x 100 = 20.85%