Calculations Using a Monthly Average

[kteare]

I am working with data where the # of data points in each month varies, for this reason when we try to sum up and average the Operational Uptime over a full year the calcuations weight the data differently and give us a number that isn't the correct calculation.  Essential what I want to to is get the Operational Uptime % by month and then use that number to trend by month and average out over any given time period (ie 2017)

The calculations Im using are as follows:

Operational Uptime % = CALCULATE('ARU Data'[Runtime %]+'ARU Data'[No Demand %])

Runtime % = CALCULATE(DIVIDE('ARU Data'[Calendar Hours]-'ARU Data'[Asset Availability]-'ARU Data'[Asset Reliability]-'ARU Data'[Asset Utilization],'ARU Data'[Calendar Hours],0) )

No Demand % = CALCULATE(DIVIDE('ARU Data'[Alternate or Intermittent Downtime],'ARU Data'[Calendar Hours],0))+0

How would I convert these calculations to show a value per month?

Thanks