Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Using the FORECAST Function.

Using the FORECAST Function

Written by Allen Wyatt (last updated October 2, 2023)
This tip applies to Excel 2007, 2010, 2013, 2016, 2019, and 2021


The FORECAST function can be used whenever you have an existing set of data pairs (x-values and y-values) and you want to calculate an estimated y-value to a new x-value. Excel performs a linear regression based on the existing values and then inserts the x-values into the expression for the regression which gives you a y-value. The new x-value can have any value and is not restricted to be larger than the existing x-values.

The FORECAST function uses the following syntax:

=FORECAST(X, Yrange, Xrange)

In this usage, X is the X value for which you want FORECAST to return a Y value. The Yrange and Xrange parameters are sets of know Y and X values.

As an example, let's say that you are going on a diet, and you decide to keep track of your weight each day. Every day you enter the date into column A and the weight for that day in column B. After getting about 10 days or so of measurements, you can use these data pairs to forecast when you will hit your target weight. If your target weight is 160 lbs., you could use the following formula:

=FORECAST(160, A2:A11, B2:B11)

The result is the anticipated date when you will reach the target weight. (This is, admittedly, a very simplistic example. Unless your metabolism is abnormal, your weight loss won't follow a straight line; it will likely decrease over time.)

Excel calculates the "trend line" (using linear regression) of the points in A2:B11 (i.e., it assumes there is a linear relationship between the dates and the weights. (This trend line is the same as you would get from plotting the data pairs and adding a trend line to the chart.)

The suitability of the FORECAST function to what you are trying to accomplish is directly tied the characteristics of the data you are working with. Suppose, for example, that you have data that increases by 5% per month over time, and you want to forecast how that data is likely to progress in the future. In such a situation you wouldn't want to use FORECAST because it works on linear data, and a 5% increase per month is not linear—it is exponential. Fitting a linear trend to an exponential data set results in an underestimation when you forecast the data. Instead you should use the GROWTH function as it is better suited for your data.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (9176) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, and 2021. You can find a version of this tip for the older menu interface of Excel here: Using the FORECAST Function.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company. ...

MORE FROM ALLEN

Getting Rid of Persistent Templates

Word uses an open interface that allows add-ons and other programs to expand the way that Word works. Sometimes remnants ...

Discover More

Adjusting Column Width from the Keyboard

It's easy to adjust the width of table columns using the mouse, but what if you don't want to use the mouse? Adjusting ...

Discover More

Putting Tables within Margins

When you first insert a table in your document, it extends from margin to margin. Later, after a bunch of editing and ...

Discover More

Best-Selling VBA Tutorial for Beginners Take your Excel knowledge to the next level. With a little background in VBA programming, you can go well beyond basic spreadsheets and functions. Use macros to reduce errors, save time, and integrate with other Microsoft applications. Fully updated for the latest version of Office 365. Check out Microsoft 365 Excel VBA Programming For Dummies today!

More ExcelTips (ribbon)

Determining Columns in a Range

If you need to know the number of columns in a particular range, you can use the COLUMNS worksheet function. This tip ...

Discover More

Using the XIRR Function

One of the financial worksheet functions provided in Excel is the XIRR function. This is used to figure out an internal ...

Discover More

Using the CONCATENATE Worksheet Function

The process of combining string (text) values to make a new string is called concatenation. Excel provides the ...

Discover More
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

View most recent newsletter.

Comments

If you would like to add an image to your comment (not an avatar, but an image to help in making the point of your comment), include the characters [{fig}] (all 7 characters, in the sequence shown) in your comment text. You’ll be prompted to upload your image when you submit the comment. Maximum image size is 6Mpixels. Images larger than 600px wide or 1000px tall will be reduced. Up to three images may be included in a comment. All images are subject to review. Commenting privileges may be curtailed if inappropriate images are posted.

What is two more than 6?

There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)


This Site

Got a version of Excel that uses the ribbon interface (Excel 2007 or later)? This site is for you! If you use an earlier version of Excel, visit our ExcelTips site focusing on the menu interface.

Newest Tips
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

(Your e-mail address is not shared with anyone, ever.)

View the most recent newsletter.