If you want to show what is going on and be able to more easily change the percentage, do this:
Original value in cell A1
In cell B1 type 4% (no equal sign, just the number 4 and the % sign) and hit enter
Cell B1 will display 4%
In cell C1 enter =A1*B1
C1 will display the percentage
Now you can enter a new percentage value in B1 without using the percent sign
and without editing a formula.