Average Calculation by 3 dimensions

[Gal123]

I'm trying to get an average value by 3 dimensions but failing to do so.

Adding an example of the data and the expected result:

As can be seen in the screenshot I'm trying to get the average size for each Warehouse by each month.

The calculation is based on (Quantity * Size )/(Total Sum of Quantity Per month).

I have tried different versions of AGGR but failed to get the expected result.

Can anyone assist?

Thanks

[Or · Accepted solution]

I only see two dimensions in your example, but this seems like it shouldn't need any aggr():

Sum(Quantity*Size) / Sum(Quantity)