Calculate a trendline forecast

Photo of Bill Jelen By Bill Jelen

Bill Jelen is the author of 24 books on Microsoft Office Excel. He is a regular guest on TechTV with Leo Laporte and the host of, which includes more than 300,000 questions and answers about Excel.

In this article, learn exactly how to use the LINEST function to calculate the formula for a trendline. This is useful, for example, when you have monthly historical sales data, and you want to predict future sales by month.

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This article is an excerpt from Learn Excel 97-2007 from MrExcel by Bill Jelen. Buy the print edition or download a free e-book edition from

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Applies to:
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