Understanding Power BI Totals: The Math, the Model, and the Misconceptions

The long-running debate around how Power BI calculates totals in tables and matrices has been part of the community conversation for years. Greg Deckler has kept the topic alive through his ongoing “broken totals” posts on social media, often suggesting that Power BI should include a simple toggle to make totals behave more like Excel. His continued campaign prompted a detailed reply from Daniel Otykier in his article No More Measure Totals Shenanigans, and earlier, Diego Scalioni explored how DAX evaluates totals internally in his post Cache me if you can: DAX Totals behind the scenes.

This blog brings all those perspectives together from a scientific and comparative angle. It looks at how totals are calculated in Power BI and compares that behaviour with Tableau, Excel, Paginated Reports, QlikView and even T-SQL. The goal is not to take sides, but to clear up the confusion around what is happening under the hood.

If you are into podcasts and prefer the audio version of this blog, I got you covered. Here an AI generated podcast for this blog. 👇

Power BI’s Broken Totals – Myth Debunked

Are Power BI Totals Really Broken?

Let’s get one thing clear right at the start, no, Power BI totals are not broken. There is no “it depends” this time. What some interpret as broken behaviour is actually how DAX and the underlying model are designed to work.

This post is not personal, it is purely scientific and technical. While I have great respect for Greg and his significant contributions to the Power BI community, I disagree with the use of the word “BROKEN.” It sounds dramatic but does not reflect the full truth. Totals in Power BI behave exactly as the model and the maths define them to. Want to know why? Keep reading.

Why this matters

When someone with Greg’s influence keeps saying totals are “broken”, it really affects how new users see Power BI. Some even start thinking the tool itself is not reliable, when what they are seeing is actually how different reporting tools do their calculations in different ways.

It helps to know the main calculation styles that these tools use:

  • Cell based: This is what you get in worksheet formulas and classic PivotTables that use Excel ranges. Totals are just simple sums of the shown items, with no model or relationships behind the scene.
  • Model driven: This is how Power BI works and also Excel PivotTables that use the Data Model (Power Pivot) or connect to a tabular dataset. Measures are calculated again for every context, so totals depend on how filters and relationships are set.
  • Query driven: Tools like Paginated Reports work this way. The report runs a query, for example SQL or DAX, gets the dataset, and then sums or averages values in the report design. The author decides how each total should be calculated.
  • Hybrid (query and context driven): Tableau fits in here. It gets the data through a query but also lets you change the level of detail and how totals behave in the visual. So sometimes it acts like a query tool and sometimes more like a model one.

Most of the confusion happens when people compare results from these tools as if they all worked the same way. Once you understand the difference between cell based, model driven, query driven, and hybrid tools, the way Power BI shows its totals starts to make full sense.

The problem that started it

Greg’s long-running example uses a small table with a single column of numbers and a DAX measure like this:

SUMX(SampleData, SampleData[Amount]) - 10

In the total row, the result shows 590, while he expects 580 (two groups of 290 each). Based on that, he argues that Power BI totals are “wrong”.

But DAX is only doing what it is told to do. In this measure, the subtraction of 10 happens after the total amount is calculated, not for each row. If the intention was to take 10 away per row, then the measure should be written like this:

SUMX(SampleData, SampleData[Amount] - 10)

This version gives the expected 580 because the subtraction now happens at the lowest level of detail, which is per row.

This might look like a small detail, but it is exactly where most of the confusion around totals begins. The difference is not about Power BI being wrong; it is about understanding where in the calculation the operation happens.

The math behind it

Before we look at the numbers, let’s first talk about what we are trying to do. We Greg’s small and very simple table that shows some amounts by Category and Colour:

CategoryColourAmount
ARed100
AGreen100
ABlue100
BRed100
BGreen100
BBlue100
Continue reading “Understanding Power BI Totals: The Math, the Model, and the Misconceptions”

Power BI 101, Report Authoring Tools

This is my last blog post in 2021. I wish you all a wonderful break and a happy new year.

In the first post of my Power BI 101 series, we learnt that Power BI is a data platform containing various tools and services. We also explained the currently available subscriptions within the Power BI platform. The focus of the second post of this series is on what we should learn to achieve our goals more efficiently. In this post, we focus on the reporting tools available to us according to our subscription plan. From this post onwards, we discuss more specific aspects of the Power BI platform.

We learnt so far that Power BI is not just a reporting tool to build sophisticated reports; it is indeed a platform supplying a wide range of features from data preparation, data modelling and data visualization to contribute to an organisation’s data analysis journey in many ways such as sharing datasets, reports, and dashboards. All of these are possible only if we take the correct steps in building our Power BI ecosystem. But, it is very true that Power BI gives us the flexibility to create professional-looking and eye-catching visualisations providing easy to understand insights around a subject. The most renowned tool within Power BI is Power BI Desktop, but it is not the only tool available to us to create reports. Besides, Power BI Desktop reports are not necessarily the best answer to all business requirements. In fact, the business requirements define the Power BI architecture that supports those requirements. Based on the architecture, organisations decide to acquire a certain subscription plan, and based on the subscription plan, we have various reporting tools available to us. At this point, you might ask, “well, what architecture supports my organisation requires?”. Let’s answer that question in a future blog post.

For the purpose of this blog post, it is enough to know what reporting tools are available under which subscription plans. Let’s get started.

Reporting tools available in Power BI

As mentioned earlier, there are various reporting tools available to us. Let’s first see what reporting tools are available to us regardless of the subscription plans. Then we will look at the subscription plans supporting those tools.

Power BI Service

Power BI Service is a SaaS (Software as a Service) offering from Microsoft in the cloud. The users within an organisation, depending on their access rights, may create reports directly in Power BI Service. The users can also securely share and distribute those reports. While creating or editing reports is possible in Power BI Service, it is strongly recommended to avoid this method for several reasons. The most obvious one is that the changes we make to a report may soon get overwritten by someone else that republishes the same report from Power BI Desktop. Check this blog post from SQLChick to see why you should avoid creating or editing reports directly from Power BI Service. The reports are downloadable in PBIX format. 

You can access Power BI Service here.

Power BI Desktop

It is a desktop application built for data preparation, data modelling and data visualisation. If you like to learn about data modelling with Power BI, check out my book here. We can use Power BI Desktop to connect to more than 250 different data sources, preparing, transforming and cleansing that data and at lastly visualising the data. Power BI Desktop is the predominant and most renowned report authoring tool available in the Power BI platform. It has many more functionalities and is more flexible than Power BI Service. For instance, setting up Role Level Security (RLS) is not available in Power BI Service. The file format of the reports created in Power BI Desktop is PBIX. 

Download Power BI Desktop from here.

Power BI Report Builder (Paginated)

Paginated reports aka pixel-perfect reports are formatted in a way to fit perfectly on a page. That report page might later be printed. We have exact control over page formatting to display our data in tables or charts. The reports are not as interactive as the reports created in Power BI Desktop.

Paginated reports are based on RDL technology which is standard report format in SQL Server Reporting Services (SSRS). The tool for developing a paginated report in the Power BI ecosystem is Power BI Report Builder. The reports file type is RDL. We can currently publish Paginated reports only to a Workspace that is backed with either a Premium Per User (PPU) or a Premium Capacity. 

Download Power BI Report Builder from here.

Power BI Desktop Optimised for Report Server (RS)

Power BI Report Server (PBIRS) is an on-premises server capable of rendering Power BI report files (PBIX). If we have a PBIRS up and running within our organisation and we require to publish Power BI reports to PBIRS, then we will need to create our reports in a special edition of Power BI Desktop which is optimised for PBIRS. This edition is different from Power BI Desktop, which we usually use to create and publish our reports to Power BI Service. For instance, Power BI Desktop RS does not include the preview features we used to see in Power BI Desktop until those features are released. Building reports in Power BI Desktop RS guarantees that the reports are fully functional after being deployed to our PBIRS. We can install Power BI Desktop and Power BI Desktop RS side-by-side on the same machine. 

Download Power BI Desktop RS from here.

Continue reading “Power BI 101, Report Authoring Tools”

Power BI Ecosystem Report Authoring Tools Demystified

Power BI Reporting Tools Confusion

There are a lot of discussions these days around Power BI tools to create reports and for sure many of you may have already downloaded and worked with some of them if not all of them. You may already think that some of the tools’ names are confusingly similar. I recently had an interesting conversation with a fellow who has a lot of SSRS report writing background. I was talking about Paginated reports and said, I downloaded the latest version of Power BI Report Builder… that he immediately said, wait for a second…

  • John: Power BI Report Builder? Oh I see, that’s the one that you can create paginated reports with then you can deploy those reports into an SSRS instance.
  • me: NOPE! That’s not the case I’m afraid.
  • John: Oh I know, I meant Power BI Report Server, you can deploy the reports to an instance of Power BI Report Server. I knew it!
  • me: NO! That’s not what I’m talking about…
  • John: What the…?

I bet some of you had a similar conversation with a friend or a customer. OK, in this post I explain a little bit about report authoring tools available to you and your organisation to get the most out of your Power BI ecosystem.

Here is a list of all reporting tools currently available to you:

  • Power BI Service: It is a SaaS (Software as a Service) offering from Microsoft in the cloud. The users in an organisation, based on their access rights, may be able to create and publish data, reports, dashboards in Power BI Service. The users can also schedule data refreshes on the published data as well as securely sharing and distributing the contents. While creating or editing reports is possible in Power BI Service, it is strongly recommended to avoid this method for several reasons. The most obvious one is that the changes you make in a report may be soon get overwritten by someone else that republishes the same report from Power BI Desktop. Check this blog post from SQLChick to see why you should avoid creating or editing reports directly from Power BI Service. The reports are downloadable in PBIX format. Use Power BI Service here.
  • Power BI Desktop: It is a desktop report authoring tool that can be used to connect to, or loading data from, varies types of data sources, preparing, transforming and cleansing that data and at last visualising the data. Power BI Desktop is the predominant report authoring tool with a lot more functionalities and flexibility than Power BI Service. For instance, setting up Role Level Security (RLS) is NOT available in Power BI Service. The format of the report file is PBIX. Download Power BI Desktop from here.
  • Power BI Report Builder (Paginated): Paginated reports aka “pixel perfect reports”, as the name resembles, are formatted in a way to fit perfectly on a page. That report page might later be printed. You have exact control over the page formatting to display your data in tables or charts. The reports are not as interactive as Power BI Desktop reports are. Paginated reports are based on RDL technology which is standard report format in SQL Server Reporting Services. The tool for developing paginated report in Power BI ecosystem is Power BI Report Builder. The reports file type is RDL. You can currently publish Paginated reports only to a Workspace that is backed with a premium capacity. Download Power BI Report Builder from here.
Continue reading “Power BI Ecosystem Report Authoring Tools Demystified”