DAX Guide
The free reference for every DAX function used in Power BI and Excel's data model, maintained by SQLBI. Each function has syntax, clear examples and notes on how it behaves with filter and row context, which the official docs often leave out.
Cheat sheet
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What it is
DAX Guide is a free reference for the DAX language (Data Analysis Expressions), the formula language behind measures and calculated columns in Power BI, Excel Power Pivot and Analysis Services. It is maintained by SQLBI, a small team well known in the Power BI world for their books and articles on DAX. The site covers more than 600 functions grouped by category (aggregation, date and time, filter, logical, text, statistical and more), plus operators, statements and data types.
Why it is better than searching
For each function it shows the syntax, the parameters, the return value, examples you can run, and which products and versions support it. It also flags behaviour that trips people up, such as whether a function triggers context transition or iterates row by row. Those notes are exactly what you need when a measure returns a number that looks wrong.
How to use it
- Keep it open while you write measures. Look up every function the first few times you use it, especially CALCULATE, FILTER, ALL, SUMX and the time intelligence functions.
- Read the examples, then rewrite them against your own model. Copying a measure you do not understand is the fastest way to publish a wrong number.
- When a result surprises you, check the notes on filter context before rewriting the measure.
Is it worth your time?
Yes, if you chose Power BI. It is a reference, not a course: learn the ideas first (Microsoft Learn's modelling path is a good start), then use DAX Guide daily. SQLBI also publishes free articles and paid courses; the reference itself is free.
Prerequisites
A data model in Power BI Desktop with at least a fact table and a date table, and a basic understanding of measures. Without a model, DAX examples are hard to follow.
Common questions
Is DAX like Excel formulas? The syntax looks similar, but DAX works on whole tables and columns filtered by the report, not on individual cells. That difference is the main thing to learn.
Do I need to know all 600 functions? No. A few dozen cover most business reports. Learn CALCULATE and filter context properly and the rest become easier.
Does it cover Power Query? No. Power Query uses a different language (M). DAX Guide is only for DAX.
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