Chart design for slides: one clear message per chart

A chart in a report can afford to be detailed. Readers can lean in, study the axes and come back to it later. A chart on a slide gets a few seconds while you’re talking. That changes almost everything about how it should be designed.

The single most useful rule is simple: each chart on a slide should make one point, and the audience should be able to see that point without you explaining the chart first. Here’s how to get there, one decision at a time.

Write the message before you make the chart

Most weak slide charts start in the spreadsheet. Someone selects a range, inserts the default chart and pastes it in. The chart shows the data, but it doesn’t say anything.

Start instead by writing the sentence you want the chart to prove. For example:

• “Enquiries doubled after we added the evening batch.”
• “Delhi is now our largest region, overtaking Mumbai this year.”
• “Costs stayed flat while revenue grew.”

That sentence becomes the slide title. If you can’t write it, you’re not ready to make the chart yet. You might need a table in the appendix instead, or a different slice of the data.

Match the chart to the claim

Once you know the message, the chart type usually follows from it.

If your message is about…	Try…
Change over time	A line chart, with the line that matters highlighted
Comparing a few items	A bar chart, sorted from largest to smallest
One item against a target	A single bar or number beside the target line
Parts of a whole, with few parts	A stacked bar, or a simple bar chart of shares
A relationship between two measures	A scatter plot with the key points labelled

Be wary of pie charts with many slices, 3D effects and dual axes. They can be made to work, but they ask the audience to do extra decoding, and a slide rarely gives them the time.

Cut everything that doesn’t help the point

Default charts carry a lot of extra ink. Go through yours and remove what isn’t earning its place:

• heavy gridlines (keep a few light ones, or none)
• borders and background fills
• decimal places nobody needs
• a legend, if you can label the lines or bars directly
• data series that aren’t part of this slide’s message

That last one is the hardest. If a chart shows eight product lines but the slide is about one of them, consider showing that one against the total, or against its nearest rival, and moving the full breakdown to a backup slide.

Use one colour to point

Colour is your quickest way to direct attention. Make most of the chart a calm neutral, such as a mid grey, and use one accent colour for the bar, line or point that carries your message. When every series has its own bright colour, the audience has to work out which one matters.

Keep that accent colour meaning the same thing across the deck. If orange means “our team” on slide four, it shouldn’t mean “competitor” on slide nine. There’s more on choosing colours that read well on a projector in contrast and colour on slides.

Make the labels readable from the back

Chart text is usually the smallest text in a deck, and the first to become unreadable on a shared screen. Treat axis labels, data labels and annotations as body text, not footnotes. If labels collide at a readable size, that’s a sign there’s too much data on the chart, not that the font should shrink.

A short annotation can do a lot of work. A small label reading “evening batch added” at the point where the line rises tells the story faster than a paragraph below the chart.

Build up a complex chart in steps

Sometimes you do need to show something richer, like a comparison across several years and regions. Rather than revealing it all at once, build it:

1. Show the axes and the first series, and explain what you’re looking at.
2. Add the comparison series.
3. Highlight the point you want people to remember.

This can be done with separate slides that each add one layer, which also makes the deck easier to read later without animations.

A quick test for every chart

Before you finalise a chart, show the slide to someone for about five seconds, then hide it and ask what they took away. If their answer matches your title, the chart works. If they describe the chart (“it’s some bars about regions”) rather than the message, simplify again.

For a wider look at the mistakes that tend to travel with weak charts, see common slide design mistakes and how to fix them.

Bringing it together

A good slide chart is less about the software and more about restraint. Decide the message, choose the chart that shows it, remove the clutter, highlight one thing and make the labels big enough to read. Do that for each chart and your data slides will start doing their job: backing up what you say, quickly and clearly.

If you’d like a second opinion on which charts in your deck are hard to read, PPT Grader can flag them alongside the rest of its feedback.