How do I set up this very specific conversion report?

#Reports & Dashboards #Salesforce Developer #Sales Cloud

For reference, I do not work in sales, I am the salesforce admin for our company. Our sales director has asked me to set up this report and I'm not sure how to do it.

Essentially we need to run a report that takes opps won this month, and compares them to leads converted this month to give a percentage.

The exact requirement is a little specific so I'll use a data set to explain:

Opportunity Name    Closed Date    Converted Date
Opp 1               01/10/2021     25/09/2021
Opp 2                              01/10/2021
Opp 3                              01/10/2021
Opp 4               01/10/2021     01/10/2021
Opp 5                              01/10/2021

Assuming "this month" is October, in the above data set we have the following  Opp 1 and 4 are closed this month, so the "Opps Closed" is 2.

Opp 2, 3, 4, and 5 are converted this month, so the "Leads Converted" is  4.

Therefore the calculation I'd use is (2/4)*100 as a percentage (which is 50%).

I've tried the following as a summary level formula:

WON:SUM/RowCount

However "RowCount" also includes the won Ops in the conversation, so it does (2/5)*100 which is not what we want.

I also tried the following:

WON:SUM/(RowCount-WON:SUM)

This time however, it doesn't account for the fact that some Won Opps are also converted in the same month, and therefore does (2/3)*100.

Any help on this would be appreciated.