The FORECAST function 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.
- The FORECAST function has been replaced in Excel 2016 with the FORECAST.LINEAR function.
|x||The data point for which you want to predict a value|
|known_y’s||The dependent array or range of data|
|known_x’s||The independent array or range of data|
|1||Known Y||Known X||Formula||Result||Notes|
|2||8||17||=FORECAST(30,A2:A5,B2:B5)||1.25||Predicts a value for y given an x value of 30|
Usage note: use this function to predict future sales, inventory requirements, or consumer trends.
Common Function Error(s)
|Problem||What went wrong|
|#VALUE!||Occurs if the supplied future value of x is non-numeric|
|#N/A||Occurs the supplied known_x’s or known_y’s arrays are empty or are of different lengths|
|#DIV/0!||Occurs if the variance of the supplied known_x’s evaluates to zero|
The FORECAST function calculates a new y-value using the simple straight lin equation for FORECAST is where
and the values of and are the sample means (averages) of the known x- and known y-values.