Understanding Data Types in Power BI

Data types define how values are stored, processed, and calculated. If the data type is incorrect, calculations may fail, visuals may behave unexpectedly, and insights may become inaccurate.
Before creating dashboards or writing DAX formulas, understanding data types is essential.

Why Data Types Matter

Consider this example:

• Revenue stored as text → You cannot sum it.
• Date stored as text → Time intelligence functions will not work.
• Percentage stored as a whole number → Results become misleading.

Power BI relies on data types to:

• Perform accurate calculations
• Enable sorting and filtering
• Apply aggregations correctly
• Optimize report performance

Correct structure leads to correct insight.

Where to Find Data Types in Power BI

To view or modify data types:

1. Open Power BI Desktop
2. Click Transform Data to open Power Query Editor
3. Select a column
4. Click the data type icon in the column header
5. Choose the appropriate data type

You can also modify data types from the Modeling tab in Report View.

                                                         In the Power Query editor. 

                                                        

                                                       In the Power BI Desktop in Table view.

Major Data Types in Power BI

Power BI supports multiple data types. Each serves a specific analytical purpose.

1. Decimal Number

• Stores numeric values with decimal points
• Used for financial data, measurements, taxes, and prices
• Supports precise mathematical calculations

E.g., total amount = 1786.9874

2. Fixed Decimal Number

• Stores numbers with fixed precision
• Maintains consistent decimal places
• Commonly used for currency calculations
• This prevents floating-point rounding issues.

E.g., total amount = 1786.99

3. Whole Number

• Stores integers without decimal values
• Used for counting, indexing, and identifiers

Example: Quantity, Employee ID (numeric), Order Count

4. Percentage

• Displays numeric values as percentages
• Used for ratios, growth rates, and performance metrics

E.g., Profit Margin %, YoY Growth %

5. Date/Time

• Stores both date and time in a single value
• Used for event logs, timestamps, and transactions

E.g., 23.02.2026 12:00

6. Date

• Stores only the date
• Used for daily, monthly, and yearly analysis
• Ideal for trend analysis.

7. Time

• Stores only time of day
• Used for analyzing hourly patterns

Example: Store opening hours

8. Date/Time/Timezone

• Stores date and time with timezone information
• Used in global reporting environments
• Ensures consistency across regions.

9. Duration

• Stores the length of time between two events
• Used for measuring processing time or task duration

Example: Order processing time

10. Text

• Stores alphanumeric values and characters
• Used for descriptive or categorical fields

Example: Customer Name, Product Category

11. True/False (Boolean)

• Stores logical values: True or False
• Used in conditional logic and filtering

Example: IsActive, IsDelivered

12. Binary

• Stores non-text data such as images or files
• Used for managing documents and multimedia data

How to Detect Data Types in Power BI

When data is loaded into Power BI, it automatically detects data types.
To verify:

1. Go to Home → Transform Data
2. Open Power Query Editor
3. Check the icon in each column header

The icon represents the assigned data type.
If Power BI assigns an incorrect data type, it can be changed manually.

How to Change Data Types in Power BI

Power BI does its best to detect data types automatically. However, inconsistencies in the dataset may result in incorrect assignments.

There are two main methods to change data types:

Method 1: Using Power Query Editor

• Open Power BI Desktop
• Go to Home → Transform Data
  
• Select the column
• Navigate to Transform tab
  
• Click Data Type dropdown
  
• Choose the correct type
• Click Close & Apply
  

Power Query will validate the change and notify you if errors occur.

Method 2: Change Data Type in Table View

After loading the data, you don’t always need to go back to Power Query. Power BI allows you to modify data types directly inside the model.

Steps

• Go to Table View (Data View) from the left panel in Power BI Desktop.
• Select the required table.
• Click on the column you want to modify.
  
• Navigate to the Modeling tab in the ribbon.
• Choose the appropriate data type from the dropdown.

Power BI will instantly apply the change to the selected column.

Why Data Types Matter

Choosing the correct data type ensures:

• Accurate aggregations
• Proper filtering and sorting
• Correct DAX calculations
• Improved performance
• Reliable visualizations

Incorrect data types may cause:

• Calculation errors
• Incorrect totals
• Performance issues
• Misleading insights

Best Practices

• Always verify data types after loading data
• Use Fixed Decimal for currency
• Avoid storing numbers as text
• Ensure date fields are properly formatted
• Clean inconsistencies before changing types