Best DAX Practices in Power BI

In this blog, you will learn the best practices for writing DAX in Power BI. Writing efficient and optimized DAX not only improves report performance but also makes your models easier to manage and scale.

Let’s explore the best techniques for writing clean, fast, and professional DAX!

1 – Use Measures Instead of Calculated Columns

Why?

• Measures are calculated only when needed, based on report context-keeping your model efficient.
• Calculated Columns increase data model size and can slow down performance, especially with large datasets.

❌ Bad Practice: Using a Calculated Column

TotalPrice = Sales[Quantity] * Sales[UnitPrice]

• Adds extra storage to your data model.
• Increases file size and refresh time.

✅ Best Practice: Using a Measure

TotalPrice = SUMX(Sales, Sales[Quantity] * Sales[UnitPrice])

• Only calculates when used in visuals.
• Optimizes performance and keeps the model lean.

2 – Avoid Repeated Calculations — Use Variables (VAR)

Why Use Variables?

• Improved Readability: Makes your DAX code cleaner and easier to understand.
• Better Efficiency: Stores results temporarily and prevents recalculating the same expression multiple times.

❌ Without Variables: Bad Practice

Profit_Margin = 
(SUM(Sales[Revenue]) - SUM(Sales[Cost])) / SUM(Sales[Revenue])

• Repeats the SUM(Sales[Revenue]) calculation twice.
• Slower performance with larger datasets.

✅ With Variables : Best Practice

Profit_Margin = 
VAR TotalRevenue = SUM(Sales[Revenue])
VAR TotalCost = SUM(Sales[Cost])
RETURN
DIVIDE(TotalRevenue - TotalCost, TotalRevenue)

• Calculates each value just once.
• Makes the code cleaner, faster, and easier to maintain.

3 – Use DIVIDE Instead of the / Operator

Why Use DIVIDE?

• Prevents Division by Zero Errors: Automatically handles cases where the denominator is zero.
• Improves Performance: More efficient and optimized than the / operator.

❌ Bad Practice: Using the / Operator

Profit_Percentage = SUM(Sales[Profit]) / SUM(Sales[Revenue])

• Can result in errors if SUM(Sales[Revenue]) is zero.
• Doesn’t handle missing or blank values well.

✅ Best Practice: Using the DIVIDE Function

Profit_Percentage = DIVIDE(SUM(Sales[Profit]), SUM(Sales[Revenue]), 0)

• Safely returns 0 when Sales[Revenue] is zero or blank.
• More efficient and error-free.

4 – Use CALCULATETABLE Instead of FILTER for Table Filtering

Why?

• Better Performance: CALCULATETABLE applies filters at the table level, making it faster and more efficient.
• FILTER Works Row-by-Row: It evaluates each row individually, which can slow down performance on large datasets.

❌Bad Practice: Using FILTER

HighSales = 
FILTER(Sales, Sales[Revenue] > 1000)

✅Best Practice: Using CALCULATETABLE

HighSales = 
CALCULATETABLE(Sales, Sales[Revenue] > 1000)

Note: CALCULATETABLE and Filter—you can use either one depending on the situation.

5 – Avoid Using ALL in Measures Unnecessarily

Why?

• ALL() removes context — which is not always needed.
• Overuse can lead to unexpected results and slow calculations.

❌Bad Practice

TotalSales = CALCULATE(SUM(Sales[Revenue]), ALL(Sales[Region]))

✅Best Practice (Use only if needed)

TotalSales = CALCULATE(SUM(Sales[Revenue]))

6 – Optimize Time Intelligence with Date Tables

Why?

• Date tables simplify time-based calculations.
• Ensure you mark the date table as a “Date Table” in Power BI.

Create Date Table

DateTable = CALENDAR(MIN(Sales[OrderDate]), MAX(Sales[OrderDate]))

7 – Use LOOKUPVALUE Carefully

Why?

• LOOKUPVALUE can cause performance issues with large datasets.
• Prefer relationships and RELATED() instead.

❌Bad Practice: LOOKUPVALUE

ProductCategory = LOOKUPVALUE(Category[CategoryName], Category[CategoryID], Sales[CategoryID])

✅Best Practice: Using Relationships

ProductCategory = RELATED(Category[CategoryName])

8 – Avoid Nested IFs — Use SWITCH Instead

Why?

• SWITCH() is more readable and faster than multiple IF statements.

❌Bad Practice (Nested IF)

Sales_Category = 
IF(Sales[Revenue] > 3000, "High",
IF(Sales[Revenue] > 1000, "Medium",
"Low"
)
)

✅Best Practice: Using SWITCH

Sales_Category = 
SWITCH(TRUE(),
Sales[Revenue] > 3000, "High",
Sales[Revenue] > 1000, "Medium",
"Low"
)

9 – Keep Your Data Model Clean and Efficient

Why?

• Unnecessary columns and tables slow down your model.
• A clean data model runs faster and is easier to manage.

✅Best Practices:

• Remove unused columns and tables.
• Create calculated tables only when necessary.
• Use proper relationships (Star Schema preferred).

10 – Use FORMAT for Display, Not for Calculation

Why?

• FORMAT() converts numbers to text, which kills performance.
• Only use FORMAT() for displaying data in a specific format.

❌Bad Practice

FormattedSales = FORMAT(SUM(Sales[Revenue]), "₹#,##0")

✅Best Practice

TotalSales = SUM(Sales[Revenue])

and apply formatting in Power BI Visuals.

Thanks for reading this post! I hope you found it helpful. Feel free to share it with others or your teammates so they can benefit from it too. 😊