To add a trendline in Google Sheets, double-click your chart, open Customize in the panel on the right, then Series, and tick Trendline. It works on bar, line, column and scatter charts. If the Trendline box doesn't appear, your chart type or data doesn't support one.
A chart shows what happened week by week. A trendline shows which way things are heading, which is usually the question a client or business partner wants answered. In Google Sheets it's a tick box hidden a couple of menus deep, and once you know where to look you can add one to any suitable chart in seconds.
Add a trendline to your chart
- Open your spreadsheet on a computer and make sure you already have a chart. If not, select your data and click Insert, then Chart.
- Double-click the chart to open the chart editor on the right.
- Click Customize, then open the Series section.
- If your chart has more than one series, use the Apply to menu to pick the one you want the trendline on.
- Tick Trendline. The line appears on the chart straight away.
Google's help page adds a useful hint: if you don't see the Trendline option at all, trendlines don't work with your data. That usually means the chart is a type that doesn't support them, such as a pie chart, or the series isn't numeric.
Which charts can have a trendline
| Chart type | Trendline available? |
|---|---|
| Line chart | Yes |
| Column chart | Yes |
| Bar chart | Yes |
| Scatter chart | Yes |
| Pie, donut and most other charts | No |
Picking the right type of trendline
Linear is the default and it's right most of the time, but Sheets offers several shapes. Google describes each one by the kind of data it suits:
| Type | Use it when your data... |
|---|---|
| Linear | closely follows a straight line |
| Exponential | rises and falls in proportion to its current value |
| Polynomial | varies, with curves and bends |
| Logarithmic | rises or falls fast and then flattens out |
| Power series | rises or falls in proportion to its current value at the same rate |
| Moving average | is jumpy and you want to smooth it out |
For weekly website visits or enquiries, I'd start with linear, then try a moving average if the line looks too sure of itself. A moving average follows the bumps more closely, so it's more honest when your numbers swing around.
The setting people miss: R squared needs a legend
Under the Trendline options you can switch on R squared, which tells you how closely the line fits your data. The closer it gets to 1, the closer the fit. Here's the catch from Google's own help page: R squared is only available if you add a legend. If you're hunting for it and it's not there, turn the legend on first, then go back to the trendline settings.
Why bother? Because a trendline always draws something, even through scattered dots that have no real pattern. A low R squared is your warning that the line is more decoration than insight, and it's worth knowing before you put it in front of anyone.
Styling the trendline
- Colour, opacity and thickness: make the trendline a contrasting colour or a lighter shade so it doesn't fight with your main data.
- Label: you can label the trendline, which helps when there are two lines on one chart.
- Polynomial degree: only shows for polynomial lines. Higher degrees bend more, which can overfit a short run of data.
- Average type and periods: only show for moving averages. More periods means a smoother line.
Trendlines on more than one series
If your chart compares two things, say enquiries from two channels, you can add a separate trendline to each series. Use the Apply to menu to switch between them and tick Trendline for each one. Give them different colours, or the chart quickly becomes hard to read.
Getting the data ready first
Trendlines are only as good as the table behind them. Google's line chart guidance is to put your labels, such as dates or week names, in the first column and your numbers in the columns beside it. Keep the dates in order, don't leave blank rows in the middle, and make sure the numbers are stored as numbers rather than text. If a column of numbers sits to the left of the cell, that's often a sign Sheets is reading it as text, and the trendline option may not appear.
It's also worth giving each column a clear header. Sheets uses the first row as the series names in the legend, and you'll need that legend later if you want R squared.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
When a trendline doesn't help
With only a handful of data points, any line will look convincing. I'd want several weeks or months of data before I'd show a trendline to a client. And remember it describes the past: it's a guide to direction, not a promise about next quarter.
What I'd do
Add a linear trendline to your line or column chart, switch on the legend so you can check R squared, and only keep the line if the fit is reasonable. If the data is jumpy, a moving average tells the story better. If you're still choosing a chart, my guide to making a graph in Google Sheets walks through the options, and a scatter plot is the chart I'd pair a trendline with most often.
Frequently asked questions
How do I add a trendline in Google Sheets?
Double-click the chart, click Customize, then Series, and tick Trendline. Use Apply to if you want it on one particular series.
Why can't I see the trendline option in Google Sheets?
Trendlines only work on bar, line, column and scatter charts. If the option is missing, your chart type or data doesn't support one.
How do I show R squared on a Google Sheets trendline?
Turn on the chart legend first. R squared is only available when the chart has a legend, then you can switch it on under the trendline settings.
Can I add a trendline to a bar chart in Google Sheets?
Yes. Google lists bar charts alongside line, column and scatter charts as chart types that support trendlines.
Which trendline type should I choose?
Start with linear for data that follows a straight line, and try a moving average if your numbers jump around a lot.
