How to Use Variables in DAX in Power BI: Simple Guide

In Power BI, use VAR to declare a variable inside a DAX formula and RETURN to output its value. Variables help store intermediate results to make formulas easier to read and improve performance.

Syntax

The basic syntax to use variables in DAX is:

• VAR: Declares a variable and assigns it a value.
• RETURN: Specifies the expression that uses the variable(s) and returns the final result.

You can declare multiple variables by repeating VAR lines before the RETURN statement.

DAX

MeasureName =
VAR VariableName = Expression
RETURN
    VariableName

Example

This example calculates the total sales and then applies a 10% discount using a variable to store the total sales amount.

DAX

Discounted Sales =
VAR TotalSales = SUM(Sales[Amount])
RETURN
    TotalSales * 0.9

Output

If total sales are 1000, the measure returns 900

Common Pitfalls

Common mistakes when using variables in DAX include:

• Forgetting to use RETURN after declaring variables.
• Using variables outside their scope (variables only exist within the measure or calculated column).
• Declaring variables but not using them, which wastes resources.

Always use variables to simplify complex calculations and avoid repeating the same expression multiple times.

DAX

Wrong =
VAR Total = SUM(Sales[Amount])
// Missing RETURN statement

Right =
VAR Total = SUM(Sales[Amount])
RETURN
    Total * 0.9

Quick Reference

Keyword	Purpose	Example
VAR	Declare a variable	VAR Total = SUM(Sales[Amount])
RETURN	Output the result using variables	RETURN Total * 0.9
Multiple VARs	Declare multiple variables	VAR A = 1 VAR B = 2 RETURN A + B

Key Takeaways

Use VAR to declare variables and RETURN to output the final result in DAX.

Variables store intermediate results to make formulas easier to read and faster.

Always include RETURN after VAR declarations to avoid errors.

Variables exist only within the measure or calculated column where they are declared.

Use variables to avoid repeating complex expressions multiple times.