Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and Excel in Microsoft 365. 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 February 8, 2020)
This tip applies to Excel 2007, 2010, 2013, 2016, 2019, and Excel in Microsoft 365


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 Excel in Microsoft 365. 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

Copying Worksheets in a Macro

Copying worksheets (one or many) is easy to do manually. What is not well known is that it is even easy to make the ...

Discover More

Preserving Bookmarks During Replace Operations

When you do a search and replace operation in Word, it is possible that you could inadvertently wipe out a bookmark or ...

Discover More

Transposing Two Words

A common editing task is to transpose two adjacent words, so that their order is changed. While the task is common, there ...

Discover More

Excel Smarts for Beginners! Featuring the friendly and trusted For Dummies style, this popular guide shows beginners how to get up and running with Excel while also helping more experienced users get comfortable with the newest features. Check out Excel 2013 For Dummies today!

More ExcelTips (ribbon)

Exact Matches with DSUM

The DSUM function is very handy when you need to calculate a sum based on data that matches criteria you specify. If you ...

Discover More

Returning the MODE of a Range

The MODE function is used to determine the most frequently recurring value in a range. This tip explains how to use the ...

Discover More

The EDATE Function

Want to figure a date a certain number of months in the future or past? The EDATE function may be just what you need for ...

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 8 - 3?

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.