Assuming your Y and N results are in the range H2 to H21 then one formula is:

=COUNTIF($H$2:$H$21,"Y")/COUNTA($H$2:$H$21)

Format as percentage.

Regards
Rowan

"danlinksman" wrote:

I have a spreadsheet that list a planned completion date and then has an
actual completion date. I have a formula that places a Y or N depending if
production met the contractual due out date or not. What I want to do is
calculate my % effective based on the "Yes" and "No" criteria. Is there a
way?