5 axis label formatting mistakes in PowerPoint and how to avoid them

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This month, we’re taking a close look at the number formatting on your chart axis labels. We’ll run through five mistakes you can easily make if you’re relying on Excel or PowerPoint defaults, and show you how to avoid them, ensuring that your axis number formatting is always geared towards clear communication and ease of understanding for your audience.

Mistake 1: Inconsistent decimal places decrease readability

If your Y-axis tick values are less than one apart, they will naturally include decimal places. However, Excel and PowerPoint will default to displaying any whole numbers on the axis as 1, 2, etc., without decimals. This creates an inconsistency that makes it harder to read the axis labels and increases the cognitive load placed on your audience.

Solution: In the chart side panel in PowerPoint or Excel, you can go to Number and enforce a fixed number of decimal places, which will usually be 1 or 2. Or, if you’re using think-cell, you simply build the chart you need and consistent decimal places are applied as standard.

Mistake 2: Misleading choice of decimals suggests inconsistent intervals

You’ve understood that it’s good to apply consistent decimal places to your Y-axis. However, you still need to make the right choice about how many decimal places to show. For example, if your tick marks are 0.25 apart, it’s important to choose two decimal places. Otherwise, the rounded numbers displayed will make it look as though the intervals are inconsistent.

Solution: Once you’ve set the number of decimal places, PowerPoint and Excel won’t update these, even if your data changes or you adjust the tick mark interval of your Y-axis. Therefore, you should always sense-check the number of decimals on your Y-axis after your chart data is final. Alternatively, use think-cell charts that automatically adapt decimal places to display consistent intervals.

Mistake 3: Counterintuitive label intervals create confusion

It’s often good to start your line chart’s Y-axis from a value above zero in order to show trends more clearly. When doing so, Excel and PowerPoint let you choose minimum and maximum bounds, and an interval, that match your dataset. Depending on your choices, you may end up with axis labels that are not strictly incorrect, but still unfamiliar and confusing.

Solution: Ensure that your minimum and maximum bounds are divisible by the interval between labels on your Y-axis. For example, if you have an interval of 3, the Y-axis can start at 9 or 12, but starting at 10 or 11 will create a counterintuitive series of Y-axis values that is harder for your audience to process. think-cell will enforce best-practice behavior by default, even as you edit the chart or update your data.

Mistake 4: Switching to percentages without care adds unnecessary clutter

If you’ve already set your Y-axis to two decimal places, then Excel and PowerPoint will retain this when you switch to percentage formatting. This results in an unnecessary .00 on every label that contributes nothing but clutter to your chart.

Solution: If you’re building an Excel or PowerPoint chart, always take care to review the number of decimal places after switching from absolute values to percentages. If you’re using think-cell, intelligent, clutter-free setting will be automatically applied whenever you change the labels from absolute to percentage values.

Bonus tip: If you have a percentage Y-axis for a value that can’t logically exceed 100%, having a maximum bound over 100% can create a false impression and waste valuable chart space. In the chart side panel in Excel and PowerPoint, set the maximum bound to 1.0 (100%) under Axis Options, or in think-cell simply use the mouse to drag the Y-axis extent to 100%.

Mistake 5: Overly long numbers slow down audience comprehension

If your Y-axis values are in the thousands, millions or billions, writing the numbers out in full adds significant clutter, makes the values harder to quickly ingest, and shrinks the space available for the chart itself.

Solution: Use number formatting with familiar abbreviations: K for thousands, M for millions, B for billions. In Excel and PowerPoint you can achieve this with rather cryptic formatting syntax by choosing Custom under number formatting and entering the required value in the Format Code field.

For example, the format code needed to display 50,000,000 as 50M in PowerPoint or Excel is 0,,"M" – though even here you may need to manually adjust the code depending on which thousand separators and how many decimal places you want to include.

Ensure effortless consistency with think-cell

As well as the five common mistakes described, it’s easy to get thousand and decimal separators mixed up in your presentation, particularly when collaborating with international colleagues who may have different default settings.

With think-cell, it takes two clicks to instantly apply consistent decimal symbols across all your charts and tables.

Thanks for reading this month’s newsletter. If you want to learn more about axis formatting options with think-cell, you can check out our user manual.

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