How about:
=YourNumber^(1/12)

or

=POWER(YourNumber,1/12)

tj

"Mark" wrote:

Hello,

I am currently undertaking some statistical analysis in excel but have
encountered a data problem, my data is annual, and i need it monthly, hence
need to take the 12th root of the numbers, but this doesnt seem available in
excel, can you please advise

kind regards