When you create a line chart in PowerPoint, the default lines connect data points with straight segments and sharp vertices. This can make trends look jagged and less readable, especially in presentations where you want to show smooth growth or gradual change. The cause is that PowerPoint applies a straight-line connector type by default to each series. This article explains how to change the line connector type to a smooth curve so your chart lines flow naturally between points.
Key Takeaways: Smoothing Line Chart Vertices in PowerPoint
- Right-click series > Format Data Series > Fill & Line > Line > Connector type > Smooth: Changes a single data series from sharp to curved lines.
- Right-click series > Format Data Series > Fill & Line > Line > Smoothed line checkbox: An alternative method that applies a smoothing algorithm to the entire line.
- Apply the same setting to each series in a multi-series chart: Each series must be changed individually for a uniform look.
Why Line Charts Show Sharp Vertices Instead of Smooth Curves
PowerPoint line charts use a default connector type called Straight. This connector draws a direct line between each pair of adjacent data points, creating sharp angles or vertices at each point. The straight connector is designed for precise data representation, but it can make trends appear abrupt. To display a gradual progression, you need to change the connector type to Smooth or enable the Smoothed line option. Both methods modify the mathematical interpolation between points, replacing sharp corners with continuous curves. No additional add-ins or external tools are required.
Prerequisites
You need an existing line chart in a PowerPoint slide. The chart can be a standard line chart, line with markers, or any chart that uses a line series. The steps work in PowerPoint for Microsoft 365, PowerPoint 2021, PowerPoint 2019, and PowerPoint 2016. The interface may differ slightly in older versions, but the options are available in the Format Data Series pane.
Steps to Change Line Connector Type to Smooth
Follow these steps to replace sharp vertices with smooth curves for one or more data series in your chart.
- Select the data series in the chart
Click once directly on the line of the series you want to smooth. All data points on that line become selected and visible. - Open the Format Data Series pane
Right-click the selected line and choose Format Data Series from the context menu. The pane opens on the right side of the PowerPoint window. - Navigate to the Line options
In the Format Data Series pane, click the Fill & Line icon, which looks like a paint bucket. Then expand the Line section if it is collapsed. - Change the connector type
Locate the Connector type dropdown. The default is Straight. Open the dropdown and select Smooth. The line immediately updates to a curved shape between data points. - Repeat for each series in the chart
If your chart has multiple data series, click the next series line in the chart and repeat steps 1 through 4. Each series must be set individually.
Alternative Method: Using the Smoothed Line Checkbox
An alternative approach uses the Smoothed line checkbox, which applies a different smoothing algorithm. This method may produce a more rounded curve than the Smooth connector type.
- Select the data series
Click the line of the series you want to smooth. - Open Format Data Series
Right-click and choose Format Data Series. - Find the Smoothed line option
In the Fill & Line section, under Line, check the box labeled Smoothed line. The line changes to a smooth curve.
Common Issues When Applying Smooth Curves to Chart Lines
The Smooth option does not appear in the Format Data Series pane
This happens when you selected the chart area or the plot area instead of the actual data series line. Click directly on the line until you see the data points highlighted. If the chart uses a stacked line type, the connector type option is still available, but the visual result may differ because stacked lines sum values.
Smoothing changes the shape of the line too much
The Smooth connector type and the Smoothed line checkbox both interpolate curves, which can overshoot or undershoot the actual data points. If the curve distorts the data, switch back to Straight connector type and add data labels to each point so the audience sees the exact values.
Only one series is smooth when the chart has multiple series
PowerPoint applies formatting per series, not globally. You must select each series line individually and apply the Smooth connector type or Smoothed line checkbox. There is no shortcut to apply the setting to all series at once.
Line Chart Connector Types: Straight vs Smooth vs Smoothed Line
| Item | Straight | Smooth | Smoothed Line Checkbox |
|---|---|---|---|
| Connector type name | Straight | Smooth | Smoothed line (checkbox) |
| Visual appearance | Sharp vertices at each data point | Curved lines with gentle arcs between points | More rounded curve, can overshoot data points |
| Best use case | Exact data representation where every point is critical | Trend visualization showing gradual change | Presentations where a polished, flowing line is desired |
| Available for all line chart subtypes | Yes | Yes | Yes |
| Applied per series | Yes | Yes | Yes |
You can now replace sharp vertices in your PowerPoint chart lines with smooth curves using the Connector type or Smoothed line option in the Format Data Series pane. Try applying the Smooth connector type to a single series first to see the effect. For a more polished look, combine smooth curves with data labels and a clean chart style. To further refine your chart, explore the Gap Width and Series Overlap options for bar charts or the Error Bars feature for statistical data.