This article describes the formula syntax and usage of the FORECAST function (function: A prewritten formula that takes a value or values, performs an operation, and returns a value or values. Use functions to simplify and shorten formulas on a worksheet, especially those that perform lengthy or complex calculations.) in Microsoft Excel.
Calculates, or predicts, a future value by using existing values. The predicted value is a y-value for a given x-value. The known values are existing x-values and y-values, and the new value is predicted by using linear regression. You can use this function to predict future sales, inventory requirements, or consumer trends.
FORECAST(x, known_y's, known_x's)
The FORECAST function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):
- X Required. The data point for which you want to predict a value.
- Known_y's Required. The dependent array or range of data.
- Known_x's Required. The independent array or range of data.
- If x is nonnumeric, FORECAST returns the #VALUE! error value.
- If known_y's and known_x's are empty or contain a different number of data points, FORECAST returns the #N/A error value.
- If the variance of known_x's equals zero, then FORECAST returns the #DIV/0! error value.
- The equation for FORECAST is a+bx, where:
and where x and y are the sample means AVERAGE(known_x's) and AVERAGE(known y's).
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?
- Select the example in this article. If you are copying the example in Excel Online, copy and paste one cell at a time.
Important: Do not select the row or column headers.
Selecting an example from Help
- Press CTRL+C.
- Create a blank workbook or worksheet.
- In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Online, repeat copying and pasting for each cell in the example.
Important: For the example to work properly, you must paste it into cell A1 of the worksheet.
- To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.
||Predicts a value for y given an x value of 30 (10.60725)