How to Change the Size of Bar Graph in Tableau

Adjusting the bar size in a Tableau visualization can feel like a small tweak, but it has a big impact on readability and the story your data tells. Whether you're making bars thicker to command attention or skinnier for a cleaner look, mastering this setting is a fundamental skill. This tutorial will walk you through several easy-to-follow methods for controlling the size and spacing of bars in your Tableau bar graphs.

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Why Does Bar Size Matter?

Changing the width of your bars isn't just about making a chart look pretty, it's a critical part of effective data visualization. The primary goal is always clarity. Thicker, more substantial bars can make a chart feel more solid and impactful, drawing the viewer's eye to the data. Conversely, overly wide bars in a busy chart can create a cluttered, overwhelming visual that's difficult to interpret.

Here’s why taking a moment to adjust your bar sizes is worthwhile:

• Improved Readability: Well-proportioned bars are easier to read and compare. Bars that are too thin can get lost, especially on a high-resolution display, while bars that are too thick can merge, making it hard to distinguish between categories.
• Better Aesthetics: A well-formatted chart is more professional and engaging. Bar size contributes significantly to the overall balance and feel of your dashboard, making your work more compelling for your audience.
• Data Density Management: If you have many categories to display, slimming down your bars allows you to fit more information into a limited space without it looking crowded. If you have only a few categories, widening the bars can help the chart fill the space more effectively.

Ultimately, a quick adjustment can be the difference between a chart that's glanced over and one that's truly understood.

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Method 1: The Simple Size Slider

The most straightforward way to change the size of your bars in Tableau is by using the Size slider on the Marks card. This is the go-to method for quick, manual adjustments and works perfectly for most standard bar charts.

Let’s walk through it with a common example: creating a chart showing Sales by Product Category.

Step-by-Step Instructions

1. Build a Basic Bar Chart: Start by connecting to your data source. For this example, we’ll use the Sample - Superstore dataset included with Tableau.
2. Locate the Marks Card: On the left side of your worksheet, you'll see a collection of properties called the Marks card. This card controls the visual properties of the data points (or "marks") in your view. You’ll see icons for Color, Size, Label, Detail, and Tooltip.
3. Click on the Size Icon: Click on the Size icon in the Marks card. This will reveal a simple slider.
4. Adjust the Slider: Drag the slider handle to the right to make the bars wider or to the left to make them thinner. You’ll see the changes applied in real-time in your chart. That’s it!

Understanding How the Slider Works

The behavior of the Size slider can change slightly depending on the type of data on your axes.

• Discrete (Blue Pills): When your dimension on the Columns shelf (like Category) is discrete, Tableau divides the available space evenly among the categories. The slider controls what percentage of that allotted space each bar fills up.
• Continuous (Green Pills): If you were using a continuous field like a date on the axis, the slider would adjust the actual width of the bar mark relative to the axis unit (e.g., the width of a day or month). An axis will appear below the slider, allowing you to set a fixed size in axis units.

Pro Tip: For extremely small adjustments, click on the slider and then use the left and right arrow keys on your keyboard for fine-tuned control.

Method 2: Dynamic Sizing with Another Measure

What if you want the size of your bars to represent another dimension of your data? Tableau allows you to do this by dragging a measure onto the Size icon. This creates a variable-width bar chart, where the width of each bar is determined by the value of a second metric.

This is a more advanced visualization technique and should be used cautiously, as it can be confusing if not labeled properly. However, it can be powerful for showing relationships between two different measures.

Let's continue with our Sales by Category chart, but this time, let's make the width of each bar proportional to its Profit.

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Step-by-Step Instructions

1. Start with Your Bar Chart: If you don't already have it, create the same vertical bar chart with Category on Columns and Sales on Rows.
2. Drag a Measure to the Size Icon: From the Data pane on the left, find the Profit measure. Click and drag Profit directly on top of the Size icon in the Marks card.
3. See the Result: Tableau immediately resizes your bars. The bar for the category with the highest profit will be the widest, and the one with the lowest profit will be the narrowest. A legend will also appear, showing the range of profit values and how they map to the different widths.
4. Edit the Size Legend (Optional): You can fine-tune how Tableau maps the values to sizes. Click the small down-arrow on the top right of the Size Legend and select "Edit Sizes...". A dialog box will open where you can adjust how sizes are distributed, map them from a certain range, or even set a fixed starting or ending size.

This technique effectively encodes two sets of information in your bars: the height shows the total sales, while the width shows the total profit. It's a great way to quickly see if your highest-selling categories are also your most profitable ones.

Method 3: Adjusting Padding and Borders for Apparent Size

Sometimes, the issue isn't the size of the bars themselves but the amount of white space between them. By controlling the padding and dividers, you can give your bars more room to breathe, which can make them appear more distinct and less crowded.

This method doesn't technically change the bar size property but adjusts the surrounding elements to achieve a similar visual effect. It’s perfect for cleaning up a busy chart or creating a specific aesthetic.

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Step-by-Step Instructions:

1. Right-Click on the Chart: With your viz created, right-click anywhere in the empty white space of the chart view.
2. Select Format: From the context menu that appears, click Format. This will open the Format pane on the left side of the screen.
3. Go to the Borders Menu: At the top of the Format pane, click on the icon that looks like a window pane to go to the Borders settings (it’s the fourth icon from the left).
4. Adjust the Column Divider: In the Borders menu, look for the "Column Divider" section. You'll see a slider for the level of the pane. Drag this slider to the right to add a thicker, more visible border line between your bars. Set the color to white or another light color to create the illusion of empty space.

This adds padding between columns, effectively pushing your bars apart. By making the divider the same color as your worksheet background (usually white), you create clean, consistent spacing between each bar. Combine this with the Size slider from Method 1 to get the perfect balance of bar width and spacing.

Final Thoughts

By leveraging the Size slider for quick adjustments, using another measure for dynamic sizing, or tweaking the formatting for better spacing, you have complete control over how your bar charts look and feel. These techniques are fundamental for turning a basic chart into a clear, professional, and insightful piece of analysis that other people can easily understand.

Learning the ins and outs of tools like Tableau is a valuable skill, but often, the learning curve can slow you down. Simple tasks like resizing bars involve clicking through menus and understanding how different settings interact with each other. At Graphed, we remove this friction by allowing you to connect your data and build visualizations just by describing what you want to see. Instead of hunting for sliders and formatting panes, you could simply ask, "show me sales by category," and we handle the rest, letting you focus on the insights, not the tool.