5.25% is the change from 400 to 421
Calculation steps:
[( 421 - 400 ) ÷ 400] x 100 = 5.25%
Formula
Percentage change = [(421 - 400) / 400] x 100
Subtract the new number by the original number
421 - 400 = 21
21 ÷ 400 = 0.0525
0.0525 x 100 = 5.25%
Example