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If you are using Access2016 and the calculation result in the query is blank and is not displayed/reflected, in most cases the reason is that the “string” or “null” field are contained in the field to be calculated.

In that case, after converting the null value of the field into an arbitrary character string with the Nz() function as shown below, use the Val() function to convert numbers (strings) to numbers(figures) and display the calculation results in the query.
(In some cases, there is no problem just by applying the Nz() function)

Val(Nz([SampleFieldName], 0))

If a character string such as alphabet is included and cannot be calculated, use the Replace () function to convert it to an arbitrary number(character string).
And the calculation result is displayed by converting the character string to a numerical value(figures) with the Val() function.