How to Change Scale in Power BI

When you're building a report in Power BI, you expect your data to tell a clear story. However, sometimes your charts end up looking like a jumbled mess. One large spike from a viral marketing campaign can crush all your other data points down to the X-axis, making them hard to read. This article will walk you through how to take control of your charts by changing the scale in Power BI. We’ll cover how to manually set the start and end points of an axis, when and how to use a logarithmic scale, and how to add a secondary axis for comparing different types of data.

Why Is Changing the Axis Scale So Important?

Before jumping into the "how," it’s helpful to understand the "why." The default "auto" scale in Power BI works well most of the time, but it doesn't always know what story you’re trying to tell. A quick adjustment can be the difference between a confusing chart and a powerful insight.

Here are a few common scenarios where you'd want to change the axis scale:

• Dealing with Outliers: Let's say your website traffic is usually steady at around 5,000 visitors per day, but one day a blog post went viral and you got 100,000 visitors. On an automatically scaled chart, that one spike will flatten all the other days, making it impossible to see the normal, smaller fluctuations. By setting a more reasonable maximum value for your axis (say, 10,000), you can exclude the outlier to better analyze your typical performance.

• Highlighting Subtle Differences: Imagine you're comparing the monthly sales of three similar products that all sell between $50,000 and $55,000. If Power BI sets the axis scale from 0 to $60,000, the bars on your chart will look almost identical. By changing the scale to start at $45,000 and end at $55,000, you zoom in on the action and make the performance differences between the products much more obvious.

• Improving Readability and Context: Sometimes you need to set a scale baseline for context. For example, if your company’s sales goal is $1 million for the quarter, you might set the maximum axis value to $1.2 million, even if your actual sales are only at $800,000. This visually shows how far you are from the goal and provides a clear performance benchmark for anyone reading the report.

Controlling Your View: How to Set a Custom Start and End on the Y-Axis

The most common and straightforward adjustment you’ll make is manually setting the minimum and maximum values for your vertical (Y) axis. This is the perfect solution for handling outliers or zooming in on specific data ranges.

Let's walk through it step by step.

How to Manually Adjust the Axis Range

1. Select Your Visual: First, click on the chart you want to modify in your Power BI reporting view. This will activate the Visualizations pane on the right side of your screen.

2. Open the Formatting Options: In the Visualizations pane, you’ll see a few icons at the top. Click on the one that looks like a paintbrush, which is the Format Your Visual icon.

3. Find the Y-Axis Settings: In the list of formatting options that appears, scroll down and find the Y-axis section. Click to expand it. If your Y-axis is turned off, you’ll need to toggle it on first.

4. Set Your Custom Range: Inside the Y-axis options, you'll see a subsection called Range. Here, you'll find input boxes for Minimum and Maximum. By default, they are set to "Auto."

5. Enter Your Values: Simply type your desired starting value into the Minimum box and your desired ending value into the Maximum box. For example, to zoom in on data between 1,000 and 5,000, you would type "1000" in Minimum and "5000" in Maximum.

Once you enter the numbers, your chart will instantly update to reflect the new scale. It’s that easy.

Pro Tip: Reverting Back to Auto-Scale

If you make a change and decide you want to go back to Power BI’s default settings, you don't have to guess what the original values were. Just go back to the Range settings and click the "Reset to default" link that appears next to the value you changed. This will switch it back to "Auto."

Handling Huge Data Ranges: Using a Logarithmic Scale

What if you're not dealing with a single outlier, but your data naturally spans several orders of magnitude? For instance, maybe you’re comparing revenue from a brand-new product line (currently at $500/month) with an established one that brings in $500,000/month. On a standard linear scale, the new product's growth would be an invisible flat line at the bottom.

This is where the logarithmic scale comes in. Instead of plotting numerical values evenly, a log scale represents values in terms of factors of 10. The jump from 10 to 100 looks the same as the jump from 100 to 1000. This is incredibly useful for visualizing growth rates and comparing data points that are drastically different in size.

How to Enable the Log Scale in Power BI

The steps are nearly identical to setting a manual range, with one small difference.

1. Select your visual and go to the Format your visual (paintbrush) pane.

2. Expand the Y-axis settings.

3. Scroll down within the Y-axis options until you see Scale Type (or a toggle labeled "Logarithmic scale" on some versions/visuals).

4. Simply switch the Scale Type from "Linear" to "Logarithmic" or toggle the switch to the “On” position. You can also pick a different base if you need to, but base-10 is generally what you're after.

A quick word of caution: Log scales can be misleading to people who aren't familiar with them, as they visually compress large differences. Be sure to clearly label your chart and make sure your audience understands what they're looking at.

Charting Apples and Oranges: How to Add a Secondary Y-Axis

Sometimes you need to plot two completely different types of data on the same chart. A classic example in marketing is a chart showing both Ad Spend (measured in thousands of dollars) and Click-Through Rate (measured as a small percentage). If you put these on the same axis, your CTR line will be a flat line stuck to the floor, completely dwarfed by the ad spend values.

The solution is to add a secondary Y-axis. This gives you a second vertical axis on the right side of your chart, with its own independent scale. With a secondary Y-axis, you can cleanly plot metrics with disparate units of measure on a single easy-to-read chart.

How to Set Up a Secondary Y-Axis

Setting this up happens in the "Fields" area of the Visualizations pane, not the "Format" area. Here’s what to do:

1. Make sure your visual is selected. Choose a visual that supports a secondary axis, like a Line and Stacked Column Chart or a Line and Clustered Column Chart.

2. With your chart active, look at the Visualizations pane where you drag fields to build your visuals.

3. In the Build a Visual section (Fields), you'll see wells for the X-axis, Column Y-axis, and Line Y-axis. By default, you'd put both values into the same wells.

4. Now, you need to find the data field corresponding to your second metric (e.g., "CTR"). Drag this field and drop it into the well labeled Secondary Y-Axis.

5. The moment you drop it in, your chart will update, and a new set of format options will appear under the Format Visual section labeled Secondary Y-Axis. Here you can adjust the range (minimum, maximum), color, and other options for that specific axis just as you did for the primary one.

Changing the X-Axis Scale from Categorical to Continuous

Last but not least, don’t forget the horizontal X-axis! The common adjustment here isn’t about setting a range or endpoint, but changing its scale type.

Power BI handles your X-axis in two main ways:

• Categorical: This treats each data point as an individual, separate label. It's perfect for things like "Product Name," "Campaign Name," or "Sales Region."

• Continuous: This treats the axis as a single, unbroken number line. This is ideal for dates or numerical values where the space between values matters.

If your data is showing as a small clump of points instead of spread out evenly, you may need to switch the X-axis scale type. To do so, you will:

1. Select your visual and go to the Format Your Visual pane.

2. Locate the X-axis settings.

3. Find the option for Type and switch it from "Categorical" to "Continuous."

This switch will enable the ability to set a minimum and maximum value, just like on the Y-axis, depending on the data type.

Final Thoughts

Taking control of your Power BI chart scale is an essential skill for creating clear, impactful reports. By learning how to adjust axis ranges, use logarithmic scales, and add secondary Y-axes, you can ensure your visualizations tell the stories you need them to tell without distortion.

While mastering these Power BI settings is a valuable skill, it’s one of those tasks where users end up clicking through menus and adjusting settings rather than actually getting insight from the data. That’s why we built Graphed. With Graphed, you don’t worry about axis ranges or scale types. You just connect your data sources like Google Analytics or Shopify, and then ask for what you want in plain English, such as: 'show me a heatmap comparing Facebook Ads expense vs. revenue for the last 30 days.' We handle the settings and visualizations automatically, letting you focus on the insights, not the settings. It’s about getting answers in seconds instead of hours, and making decisions faster.