How to Add a Trendline in Excel and Pick the Right Type

Weekly numbers jump about. One good week, two quiet ones, a spike after a newsletter goes out. A trendline cuts through that noise and draws the overall direction across your chart, so you can tell at a glance whether website visits, enquiries or followers are heading up, flat or down.

Adding one takes a few clicks. Choosing the right type takes a little more thought, and that's where Microsoft's own trendline guide is useful. I'll cover both, using Microsoft's descriptions of what each option is for.

What you need before adding a trendline in Excel

You need a chart first. Trendlines are added to a chart, not to the cells. Line charts, column charts and scatter charts are the usual homes for one, because they show values in order.

If you haven't built your chart yet, select your data, go to Insert and choose a chart type. Then come back here.

Adding a trendline in Excel for Windows

1. Click your chart to select it.
2. Go to the Chart Design tab.
3. Select Add Chart Element.
4. Point to Trendline, then choose the type you want, such as Linear, Exponential, Linear Forecast or Moving Average.

A line appears across your data.

For more choices than the short list, go to Add Chart Element, Trendline, then the options at the bottom of the menu. That opens the formatting pane, where you'll find every trendline type and its settings. Menus vary by app version, so the exact wording can differ slightly.

Adding a trendline in Excel for the web

In the browser, Microsoft describes a slightly different route:

1. Double-click the chart until the Chart pane opens on the right of the screen.
2. Select Format, then Trendline.
3. Switch the toggle on to add a trendline, or off to remove it.

From the same pane, Microsoft says you can change the trendline's name, its trend type, its style and its intercept.

Choosing the right Excel trendline type

This is where most people guess. Here's what Microsoft says each type suits, in plain terms:

Trendline type	Microsoft says it suits	Watch out for
Linear	Data that rises or falls at a steady rate	Curved data won't fit well
Logarithmic	Data that changes quickly, then levels off	Can use negative and positive values
Polynomial	Data that goes up and down	Pick an order to match the bends
Power	Data that increases at a specific rate	No zero or negative values
Exponential	Data rising or falling at constantly increasing rates	No zero or negative values
Moving average	Smoothing out bumpy data	Set a Period

For most small business charts, I'd start with Linear. It answers the simple question: overall, are we going up or down? Only try a curved type if the straight line clearly doesn't follow your data.

Setting polynomial order and moving average period

Two types need an extra setting.

Polynomial asks for an order, which is roughly how many bends the line can make. Microsoft says an Order 2 polynomial typically has one hill or valley, Order 3 has one or two, and Order 4 has up to three. Choose the lowest order that follows your data; higher orders can wiggle to fit every bump, which tells you less.

Moving average asks for a Period. That's how many points in a row Excel averages to plot each point on the line. Microsoft's example uses a period of 2. A bigger period gives a smoother line. For weekly data, a period of 4 roughly smooths a month at a time.

One extra tip from Microsoft: if you add a moving average to a scatter chart, the line follows the order of your x values, so sort your data first or the line can zigzag.

Reading the R-squared value on an Excel trendline

In the trendline formatting options you can choose to show an R-squared value on the chart. Microsoft describes it as a number from 0 to 1 that shows how closely the trendline matches your data. The closer to 1, the better the fit.

It's handy for comparing two trendline types on the same chart. If Linear gives a much lower value than Logarithmic, the curved line is probably the better description. For a chart you're sharing with a client, though, I'd often leave the number off and just let the line speak.

Why some Excel trendline types are greyed out

If Power or Exponential won't apply, check your data. Microsoft says you can't create those trendlines if your data contains zero or negative values. A single zero week, or a negative change, is enough to block them. Use Linear or Polynomial instead, or remove the zero if it was a data entry slip.

Using trendlines in business and creator reports

• Website or shop visits by week, with a Linear trendline to show overall growth.
• Email sign-ups with a Moving Average to smooth out one-off spikes.
• Follower counts across a year to see if growth is steady or levelling off.

When a chart goes into a branded slide or social graphic, it helps to match your fonts. My guide to bringing your brand fonts into Canva covers that side. And if you're tracking weekly numbers in the browser, a tick column in Google Sheets is an easy way to mark which weeks you've logged.

Removing a trendline from an Excel chart

Click the trendline itself so it's selected, then press Delete. On the web, open the Chart pane, select Format, then Trendline, and switch the toggle off.

Frequently asked questions

How do I add a trendline in Excel?

Click the chart, go to the Chart Design tab, select Add Chart Element, then Trendline, and choose a type such as Linear.

Which trendline type should I use in Excel?

Microsoft says Linear suits data rising or falling at a steady rate. Use a Moving Average to smooth bumpy data, and Polynomial for data that goes up and down.

Why can't I add an exponential trendline?

Microsoft says exponential and power trendlines can't be created if your data contains zero or negative values.

What does R-squared mean on a trendline?

Microsoft describes it as a value from 0 to 1 showing how closely the trendline matches your data. Closer to 1 means a better fit.

Can I add a trendline in Excel for the web?

Yes. Double-click the chart to open the Chart pane, select Format, then Trendline, and switch it on.