Dynamically calculating column in a table based on slicer value

Hi all,

In one of my tables I have a list of IT systems, and a column that lists, for each system, the amount of hours said system has been down or non-functional. I'm tryinng to calculate the proportion of a selected period of time that a given system was down for.

For example, if system X was down for 12 hours on the 3rd of March:

- There are 744 hours in March, so if I selected March in a slicer I would like to display that it was down for 1.612%

- There are 2160 hours in the first quarter of the year, so if i selected Q1, I'd like to display that it was down for 0.56%

- There are 8760 hours in a year, so if i selected a whole year I'd like to display that it was down for 0.14%

I am using a date table that has a column for hours, which has a value of 24 in every row. (I didn't allow for daylight savings etc as that level of accuracy wasn't necessary). When I display the amount of hours I use SUM(Hours).

My current formula is %Downtime = Downtime / SUM('Date'[Hours]). At the moment, I have 3 years worth in my date table and no matter what date range I select in the report, every %Downtime value is shown as "Downtime / 26,280".

What do I have to do to get this value to change based on the date range I select?

Thanks 🙂