Ratio Calculation

You don't need a data model for this but, if you have a model, still this formula will work. Here is the DAX measure that you can use:

Ratio = 
VAR _clientTotal =
    CALCULATE (
        SUM ( MainTable[Amount] ),
        FILTER (
            ALL ( MainTable ),
            MainTable[ClientID] = SELECTEDVALUE ( MainTable[ClientID] )
        )
    )
VAR _ratio =
    DIVIDE ( SUM ( MainTable[Amount] ), _clientTotal )
RETURN
    _ratio

Well instead of  SUM ( MainTable[Amount] ) you can create a simple measure like this and use it too:

Total Amount = SUM ( MainTable[Amount] )

Here is the screenshot of the solution:

Hope this will resolve your issue.

Best Regards,
Udit

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