299.21% is the change from 126 to 503
Calculation steps:
[( 503 - 126 ) ÷ 126] x 100 = 299.21%
Formula
Percentage change = [(503 - 126) / 126] x 100
Subtract the new number by the original number
503 - 126 = 377
377 ÷ 126 = 2.992063492063492
2.992063492063492 x 100 = 299.21%