calculating the std devation of portfolio

If I have a portfolio with hypothetical time-weighted returns by month of the following:

Jan-20 = 2%
Feb-20 = 5%
Mar-20 = 50%
Apr-20 = 6%
May-20 = -5%
Jun-20 = 0%
Jul-20 = -10%
Aug-20 = 4%
Sep-20 = 20%
Oct-20 = 7%
Nov-20 = 30%

Then in excel can I just use the standard deviation function to get a std dev of 17.2% for the portfolio, or do I need to add 1 to all of these returns and then calculate the standard deviation i.e. Jan-20 = 1.2 and so on.