What a trendline does and when you need one
A trendline is a straight or curved line that Google Sheets draws through your data points to show the overall direction they're moving. If you have sales numbers climbing month to month, a trendline makes that upward pattern visible at a glance. If website traffic is bouncing around but generally flat, the trendline shows that too.
You add a trendline to a chart you've already created in Google Sheets — it's not something you add to raw data. The trendline appears on top of your existing bars, dots, or lines, making patterns easier to spot in messy data. This is useful when you're presenting information to someone else, or when you're trying to understand what your own numbers are actually doing underneath the noise.
Trendlines work best on scatter charts and line charts. They can work on column and bar charts too, but they're less common there because the pattern is usually already clear.
Key Takeaways
- You add a trendline only to a chart that already exists in your sheet — right-click the chart and choose "Edit chart" to start.
- In the chart editor, go to the Series tab, click on your data series, scroll down to find Trendline, and choose Linear, Exponential, Polynomial, or Moving Average.
- Linear trendlines work for most situations where data is climbing or falling at a steady rate.
- You can show the equation and R-squared value on the chart itself so viewers see how well the trendline fits your actual data.
Create or open the chart you want to add a trendline to
If you don't have a chart yet, create one first. Highlight the data you want to chart (including headers), go to Insert at the top, click Chart, and Google Sheets will build a default chart. You can adjust the chart type and other settings in the chart editor that opens — for now, just get something on the page.
If you already have a chart, click on it once to select it. The chart will show a border around it and a three-dot menu will appear in the top right corner of the chart.
Open the chart editor and find the Series tab
Right-click on the chart itself (not on the data inside it) and select "Edit chart" from the menu. The chart editor panel will open on the right side of your screen. At the top of that panel, you'll see tabs: Setup, Series, Customize, and sometimes others depending on your chart type.
Click on the Series tab. You'll see a list of the data series in your chart — usually just one, but sometimes more if you charted multiple columns of data. Click on the series you want to add a trendline to.
Scroll down to Trendline and choose your type
Once you've selected your series, scroll down in the Series panel. You'll see an option called Trendline with a checkbox next to it. Check that box. A dropdown menu will appear below it showing your trendline options.
For most situations, choose Linear. This draws a straight line through your data and works when your numbers are generally climbing or falling at a steady rate. If your data curves upward or downward (like compound growth or decay), try Exponential. If it dips and rises, Polynomial might fit better. Moving Average smooths out short-term wobbles to show longer-term direction.
Once you pick a type, the trendline appears on your chart when ready. You'll see it as a line running through or near your data points.
Show the equation and R-squared value (optional)
Below the Trendline dropdown, you'll see two more checkboxes: "Show R²" and "Show equation". The R² value tells you how well the trendline actually fits your data — closer to 1 means the trendline matches your points closely, closer to 0 means it's a loose fit. The equation is the mathematical formula for the line, useful if you want to predict future values.
Check these boxes if you want them displayed on the chart. They'll appear as text on the chart itself. If the text overlaps your data and looks messy, you can uncheck them — the trendline will still be there.
Adjust the trendline appearance if needed
If you want to change the color or thickness of the trendline, look for a "Format trendline" option in the Series panel, or click on the trendline itself in the chart and a formatting menu will appear. You can make it thicker, thinner, or a different color to make it stand out from your data.
Most of the time the default appearance works fine. The trendline is usually a different color from your data series, so it's straightforward to see.
Save your chart and close the editor
Once your trendline looks right, click the X button at the top right of the chart editor panel to close it. Your chart is saved automatically — Google Sheets saves changes as you make them. The trendline will stay on your chart and move with it if you resize or move the chart around your sheet.
If you need to edit the trendline later, just right-click the chart again, choose "Edit chart", go back to the Series tab, and make your changes.
Frequently Asked Questions
Can I add more than one trendline to the same chart?
Only if you have multiple data series. Each series can have its own trendline. If you have one series with multiple data points, you get one trendline for that series. If you charted two columns of data (like sales and expenses), you can add a trendline to each column separately.
What does the R² number mean exactly?
R² is a score from 0 to 1 that shows how closely the trendline matches your actual data. An R² of 0.95 means the line explains 95 percent of the variation in your data — a very good fit. An R² of 0.5 means the line only explains half of what's happening — the data is scattered. There's no magic number; it depends on what you're measuring.
My trendline doesn't look right. What went wrong?
The most common issue is choosing the wrong trendline type. If your data curves but you picked Linear, the line won't fit well. Try Exponential or Polynomial instead. Also check that you selected the right data series — if you have multiple series, make sure you're editing the one you meant to.
Can I remove a trendline after I add it?
Yes. Right-click the chart, choose "Edit chart", go to the Series tab, click your data series, and uncheck the Trendline checkbox. The line disappears when ready.