How to Create a Data Dictionary in Power BI

Creating a Power BI report that everyone trusts and understands can feel like a tall order. When an executive asks what "Total Sales" includes and a sales manager has a different definition, confidence in your data plummets. A data dictionary solves this by creating a single source of truth for all your metrics, fields, and calculations. This article will show you exactly how to create and maintain a data dictionary for your Power BI reports to ensure everyone is on the same page.

What Exactly Is a Data Dictionary (and Why Does Your Report Need One)?

Think of a data dictionary as a formal encyclopedia for your data. It’s a centralized document that defines every element within your Power BI data model. It answers critical questions like:

• What does this field [Prod_ID] actually mean?
• How is the [Gross Margin %] measure calculated?
• Where does the [Lead_Source] data come from?
• Who is responsible for the accuracy of our sales data?

Ignoring this step is a common mistake. Without a dictionary, your Power BI reports can quickly become a "black box" that only a few people understand. This creates bottlenecks, leads to misinterpretations, and ultimately erodes trust in the very insights you’re trying to share.

The Benefits of Having a Data Dictionary

Investing a little time in creating a data dictionary pays off significantly:

• Clarity and Consistency: It ensures that "revenue" means the same thing across all reports and for every team member. This eliminates confusion and guarantees that everyone works from a shared understanding.
• Faster Onboarding: New hires or team members can get up to speed in hours, not weeks. Instead of asking you repetitive questions, they can consult the dictionary and understand the data model on their own.
• Easier Report Building: For both you and other report builders, a dictionary removes the guesswork. You'll know precisely which fields to use for your visualizations without having to hunt through tables or reverse-engineer formulas.
• Improved Data Governance: It forms the cornerstone of good data governance. By documenting data owners and sources, you create a framework for maintaining data quality and accountability.

Gathering the Right Information

Before you jump into any tools, start by gathering the necessary information. A good data dictionary goes beyond just technical names. It provides business context. For each table, column, and measure in your data model, you should aim to document the following:

• Table Name: The name of the table as it appears in the data model (e.g., DimCustomer, FactSales).
• Field Name: The proper name of the column or DAX measure (e.g., CustomerKey, [Total Revenue]).
• Business-Friendly Name: An alternative, more intuitive name for the field if the technical one is cryptic (e.g., Prod_SKU_v2 might be "Product SKU").
• Data Type: The type of data in the column (e.g., Whole Number, Text, Date, Decimal).
• Description: This is the most crucial part. Write a clear, plain-language definition of the field and its business purpose. Explain what it represents and why it's important.
• Calculation/Formula: For any DAX measure or calculated column, include the exact formula used.
• Data Source: The original source system where this data originates (e.g., Salesforce Opportunity Object, Shopify orders table, specific Google Sheet).
• Example Values: Provide a few sample values to add context (e.g., New, In Progress, Closed-Won for a status field).
• Owner: The person or team responsible for the accuracy and maintenance of that data.

Starting with a simple spreadsheet to collect this information is often the easiest first step.

3 Methods to Create Your Power BI Data Dictionary

Once you’ve gathered your information, you can implement your dictionary directly within your Power BI environment. Here are three popular methods, ranging from simple to more automated and interactive.

Method 1: The Simple Approach - Using Descriptions and Tooltips

Power BI has a built-in feature for adding descriptions to your fields, which then appear as tooltips for anyone using the report. This is the quickest way to provide in-context help to your users.

How to do it:

1. Open your Power BI file and click on the Model view icon on the left side.
2. From the Fields pane on the right, select the column or measure you want to document.
3. In the Properties pane below, you will see a text box for Description.
4. Enter your clear, business-friendly definition here. For measures, you can also paste the DAX formula for easy reference.
5. That's it! Now, when you or another user are in the Report view and hover over that field in the Fields pane, your description will pop up as a helpful tooltip.

Pros:

• Easy and fast to implement
• Built directly into the Power BI interface
• Extremely helpful for analysts using the dataset

Cons:

• Descriptions aren't easily exportable into a single document
• Inputting them can be tedious for models with hundreds of fields

Method 2: The Automated Approach - Using External Tools

For larger data models, manually entering descriptions field-by-field can be a chore. Luckily, you can use powerful free tools like DAX Studio to automatically extract the model metadata and kickstart your dictionary.

How to do it with DAX Studio:

1. Download and install DAX Studio (it’s a free, third-party tool widely used by Power BI professionals).
2. Open the Power BI file you want to document.
3. Launch DAX Studio. It will prompt you to connect to a model, your open PBIX file should appear in the list. Select it and click Connect.
4. DAX Studio provides access to Dynamic Management Views (DMVs), which contain a wealth of metadata about your model. You can query these views to pull out field information.
5. In the DAX Studio query window, run the following query to extract a list of all your tables and columns, along with their data types and any descriptions you've already added from Method 1:

EVALUATE
SUMMARIZECOLUMNS(
    'Table'[Name],
    'Table'[Description],
    'Column'[Name],
    'Column'[DataType],
    'Column'[Description]
)
ORDER BY 'Table'[Name], 'Column'[Name]

This query uses TMSCHEMA views available in Power BI. An alternative for broader compatibility is using INFO functions, like INFO.TABLES() and INFO.COLUMNS() if needed.

1. Click Run. The results will appear in the bottom pane.
2. Now, go to the Output tab and select how you'd like the results. You can export directly to a CSV or Excel file (Static).
3. This exported file becomes the foundation of your official data dictionary, which you can now flesh out with the deeper business context and share with your team.

Pros:

• Massively speeds up the documentation process
• Captures all fields at once
• Provides a structured output perfect for a formal document

Cons:

• Requires installing a free external tool
• Has some learning curve and basic comfort with running SQL queries

Method 3: The Interactive Approach - Building a Dictionary Page in Your Report

This method combines the best of both worlds: automation and interactivity. Here, you create a dedicated page within your Power BI report that acts as a searchable, filterable data dictionary.

How to do it:

1. Follow the steps in Method 2 to export your model's metadata to an Excel or CSV file.
2. Open this file and dedicate some time to writing high-quality, user-friendly descriptions for each field. This is where you add the most value. Consider adding columns for Business Owner, Data Source, etc.
3. Save this Excel file in a shared location like SharePoint, OneDrive, or a shared drive.
4. Back in your Power BI report, click Get Data and connect to the Excel file you just created. Import the data dictionary sheet as a new table in your model.
5. Create a new, dedicated page in your report and name it "Data Dictionary" or "Report Guide."
6. On this new page, add a Table or Matrix visual. Drag the columns from your new data dictionary table into the visual (Table Name, Column Name, Description, Owner, etc.).
7. Add a Slicer visual to the page and connect it to the Table Name field. This lets users easily filter the dictionary to see the details for a specific table.

Pros:

• Creates an interactive, self-service resource that lives right alongside the data
• Always available to end-users
• Promotes data literacy

Cons:

• Adds another table to your data model
• Requires refresh if you update the underlying Excel file

Best Practices for a Living, Breathing Data Dictionary

Creating your dictionary is just the first step. The real value comes from maintaining it. Here are a few tips to make sure it stays relevant:

• Keep It Simple: Write definitions in plain language. Avoid technical jargon whenever possible. The goal is for a non-technical stakeholder to understand it.
• Assign Ownership: Designate a person or team responsible for keeping the dictionary up-to-date. Without clear ownership, it will quickly fall out of date.
• Integrate It Into Your Workflow: Make updating the dictionary a standard part of your development process. When you add a new table or create an important new DAX measure, document it immediately.
• Make It Accessible: Don't bury your dictionary in a forgotten folder. By building it directly into the report (Method 3) or hosting it on a company-wide wiki, you ensure everyone knows where to find it.

Final Thoughts

Building a data dictionary is a small investment of time that pays huge dividends in data trust, team efficiency, and user adoption of your Power BI reports. By moving documentation from an afterthought to a core part of your process, you build a stronger, more data-driven culture.

While manual documentation helps bridge gaps, the real challenge is dealing with data scattered across a dozen platforms, each with its own field names and definitions. We designed Graphed to solve this by creating an intelligent semantic layer over all your connected data. When you ask a simple question in plain English, our AI already understands the context behind your metrics, eliminating the need to cross-reference a separate dictionary. It's like having a dynamic, automated data dictionary working for you in the background in real-time.