Number per month when not all months have data

[GCH_Ryan]

My data is a list of homes that will be sold and a projected date of when they will be sold. One of the columns is Gross Margin another is projected Sales Closing. I would like to have a card that shows the Gross Margin per month based on the number of months in a filtered number of years. For instance, if select 2018 on my slicer it will be SUM([GrossMargin]) / 12. If my slicer shows 2018 - 2020 the formula would be SUM([GrossMargin]) / 36. The issue I am running into is that we don't always have a home sale every month. I've tried creating a calendar table with a yyyy-mm column and relating that to my Sales Closing with a 1 to many relationship. I then created a count measure on the yyyy-mm column however when filtered by Sales Year, it only displays the count of months where there is a sale. For a stop gap I created this measure:

GMperMonth24 = CALCULATE(SUM('Future Sales'[Gross Margin]) / 24 , FILTER('Unit_Performance' , OR(YEAR(Unit_Performance[Sale Closing]) = 2018 , YEAR(Unit_Performance[Sale Closing] = 2019))))

I added that measure to a card, then disabled the interaction with the slicer on the page which works for those two years but I need to link this card to the other slicer. My idea is toreplace the  "24" with a count formula and ditch the Filter portion but I can't figure out how to get the right count of the number of total months within the selected number of years in the slicer. Any ideas? 

Edit 1

Example Report: I would like the card in Gross Margin $ per Month card in the upper left to reflect the average goss margin per month based on the number of total months in the period of years selected in the slicer. Because there are months with no sales, my Sales Closing dates are missing months and can't act as the driver for the number of months in the given year. Please let me know if there is specific sample data I can provide.

[Vvelarde · Accepted solution]

@GCH_Ryan

Hi , With your short explanation and without a sample, i assume that you want this:

NumberofMonthsSelected= (Year(LastDate(CalendarTable[Date]  ) )-Year(FirstDate(CalendarTable[Date] ) ) + 1)*12

Regards

Victor

[GCH_Ryan]

@Vvelarde This didn't work at first, and then I realized that my slicer was based on the Sales Closing Date, not the date from the calendar table. Once I made that change, this solution worked. Thank you! 

[Greg_Deckler]

Sample/example data is extremely helpful for solving these kinds of problems.

https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

[GCH_Ryan]

@Greg_Deckler Thanks for the advice, I added a screen shot and tried to more clearly explain the problem I'm facing and my desired outcome.