=COUNTIF(C2:C20,"yes")/COUNTA(C2:C20)

and format as a percentage.

--
HTH

Bob Phillips

(remove nothere from email address if mailing direct)

"npw" wrote in message
...
How do I write a formula to determine a % of "yes" responses for a range
of
cells. For example: Cells C2-C20, 12 of the 18 cells have "yes" the other
6
have "no". Cell C21 would have the % of yes. Thanks!!