How to Find Slope of Trendline in Google Sheets

A trendline in Google Sheets does more than just cut across your chart, it tells a story about the direction your data is headed. The single most important part of that story is its slope - the number that quantifies the rate of change. This guide will show you three simple ways to find the slope of a trendline in Google Sheets, so you can move from just looking at data to actually understanding it.

What is Trendline Slope and Why Should You Care?

In simple terms, the slope of a trendline is a number that tells you how much the value on your vertical axis (the Y-axis) is expected to change for every one-unit increase on your horizontal axis (the X-axis).

Think about a chart tracking your monthly website traffic:

• A positive slope (e.g., 500) means your traffic is growing. For every month that passes, you gain an average of 500 new visitors. The higher the number, the faster the growth.
• A negative slope (e.g., -150) means your traffic is declining. For every month that passes, you lose an average of 150 visitors. The more negative the number, the steeper the drop.
• A slope near zero (e.g., 5 or -10) suggests your traffic is flat. There's no significant growth or decline.

Calculating the slope turns a vague feeling ("I think things are improving") into a hard fact ("We are growing at a rate of 500 visitors per month"). This number is incredibly useful for forecasting future performance, setting realistic goals, and identifying whether your strategies are working.

Method 1: Find the Slope Visually with a Chart

The most intuitive way to find the slope is by having Google Sheets draw a trendline right on a chart and display its mathematical equation. This method is perfect for presentations and visual reports.

Let's use an example. Imagine you have data tracking website traffic for the first six months of the year:

Step 1: Create a Scatter Chart

A scatter chart is the best choice for visualizing this type of relationship.

1. Select your data, including the headers (e.g., A1:B7).
2. Go to the menu and click Insert > Chart.
3. Google Sheets will often default to a different chart type. In the Chart editor on the right-hand side, under the Setup tab, change the Chart type to Scatter chart.

Step 2: Add and Customize the Trendline

Now, you can add the trendline that will reveal the slope.

1. In the Chart editor, go to the Customize tab.
2. Click on the Series section to expand it.
3. Scroll down and check the box next to Trendline. A line will immediately appear on your chart, showing the general direction of your data points.

Step 3: Display the Trendline's Equation

This is where you get the number you're looking for.

1. While still in the Series section, scroll down to the Label dropdown.
2. Select Use Equation from the list.
3. An equation in the format y = mx + b will now appear on your chart (e.g., 691.4x + 9605).

Step 4: Identify the Slope

Remember the classic line equation from school, y = mx + b?

• m is the slope.
• x is your value on the horizontal axis.
• b is the y-intercept (where the line would cross the vertical axis if x were 0).

In our example equation, 691.4x + 9605, the slope is 691.4. This tells you that for each month that passes, your website traffic is increasing by an average of about 691 visitors.

Method 2: Use the SLOPE Function for a Direct Answer

What if you don't need a chart? If you just want the slope value itself to use in a summary table or another calculation, the SLOPE function is the fastest way to get it.

Understanding the SLOPE Function

The syntax for the function is very straightforward:

=SLOPE(data_y, data_x)

There are two key things to remember:

• data_y: This is your range of known Y values (the dependent variable, like "Visitors").
• data_x: This is your range of known X values (the independent variable, like "Month").

Crucially, you must enter the Y-range before the X-range. This is a common pitfall and the opposite of how we typically think ("X and Y"), so pay close attention to the order.

How to Use It

Using our same website traffic data, with months in column A and visitors in column B:

1. Click on any empty cell where you want the slope to appear.
2. Type the following formula:

=SLOPE(B2:B7, A2:A7)

1. Press Enter.

The cell will immediately display the result: 691.428..., the same slope we found visually from the chart's equation. The formula just gives you a more precise version without rounding.

Method 3: The Advanced Approach with the LINEST Function

For those who need more than just the slope, Google Sheets has a powerful statistics function called LINEST (short for "Linear Estimation"). This function calculates a full suite of stats for a straight line that best fits your data.

While SLOPE just gives you the slope, LINEST can also give you the Y-intercept, standard errors for both the slope and intercept, and the R-squared value, which tells you how well the trendline fits your data.

Understanding the LINEST Function

The basic syntax is similar to the SLOPE function:

=LINEST(data_y, data_x)

Like SLOPE, the Y-range comes first. However, LINEST is an array formula, meaning it outputs its results into multiple cells. By default, it returns the slope and the Y-intercept.

How to Use It

1. Click an empty cell.
2. Enter the formula using our example data:

=LINEST(B2:B7, A2:A7)

1. Press Enter.

You'll see two numbers appear in adjacent cells:

• The first cell (the one you typed in) will contain the slope: 691.428...
• The cell to its right will contain the Y-intercept: 9605

LINEST is overkill if all you need is the slope, but it’s the go-to function for anyone needing to perform a more rigorous linear regression analysis directly in their spreadsheet.

Final Thoughts

Whether you prefer a visual approach using charts or a direct calculation with formulas like SLOPE and LINEST, Google Sheets makes it simple to uncover the trend in your data. Calculating the slope turns your raw numbers into a clear story, showing you exactly how fast things are growing, shrinking, or staying the same.

Often, the biggest challenge isn't finding the trend in one dataset, but making sense of trends across a dozen different platforms - your site traffic, ad spend, sales numbers, and email engagement. Stitching it all together manually into spreadsheets takes hours. To solve this, we built Graphed to be your personal AI data analyst. You can connect all your tools in minutes and then ask questions in plain English, like "What's the trend in my Shopify sales versus my Facebook Ads spend this quarter?" and get a live, interactive dashboard instantly.