1371.43% is the change from 21 to 309
Calculation steps:
[( 309 - 21 ) ÷ 21] x 100 = 1371.43%
Formula
Percentage change = [(309 - 21) / 21] x 100
Subtract the new number by the original number
309 - 21 = 288
288 ÷ 21 = 13.714285714285714
13.714285714285714 x 100 = 1371.43%