In Excel: use =FORECAST.LINEAR(x, known_ys, known_xs) — it predicts a single value from a straight-line fit through your historical points.
On this page8
Syntax
Arguments
| Argument | required / optional | Description |
|---|---|---|
x | required | The point to predict a value for. |
known_ys | required | The observed outcomes. |
known_xs | required | The observed inputs, the same size as known_ys. |
Related functions
Select the result cell and type =FORECAST.LINEAR(.
Enter the x value you want a prediction for, then a comma.
Select the known y values, a comma, then the known x values.
Press Enter. Chart the actuals with the prediction to sanity-check the line.
What this does
FORECAST.LINEAR predicts one y for one x by fitting a least-squares line through the known points. It is identical to computing INTERCEPT plus SLOPE times x, just in one call. The newer FORECAST.ETS handles seasonal time series with exponential smoothing and needs a proper date column; the plain linear form assumes a straight-line relationship and nothing more. The legacy FORECAST still works and matches FORECAST.LINEAR. As with any regression, predictions far outside the observed range of x are extrapolation rather than forecasting. Keep the inputs visible and clearly labelled and the whole thing stays auditable — anyone who opens the file later, including you, can see at a glance exactly what feeds the result and change one assumption without hunting through the formula. For “excel forecast linear”, the reliable version is a short checking loop, not just the first command that appears to work. Run it on a deliberately small range first, watch how the affected cells change, and only then apply the same setup to the full sheet. When a formula is involved, keep the inputs labelled beside it, reference cells instead of typing values, and apply number formatting only after the result checks out. That is what makes a calculation you can defend to a CFO or an auditor useful in real work: repeatable, auditable, and not dependent on memory or luck.
A worked example
Months 1 to 24 in A2:A25 and revenue in B2:B25: =FORECAST.LINEAR(25, B2:B25, A2:A25) predicts month 25. For a seasonal series with real dates, =FORECAST.ETS(newDate, B2:B25, A2:A25) captures the repeating pattern a straight line cannot. FORECAST puts a defensible projection in a cell instead of a chart annotation, which is what a planning model needs. Check the referenced cells, argument order and result type in your workbook. Start with the worked example before changing an input, then compare the changed result with the calculation you expected. An error value or a result of a different type is a reason to inspect the inputs and arguments.
In Google Sheets
Google Sheets support for this task has not been verified. Check the function, arguments and workflow in the target product before transferring the example. Matching formula notation does not establish identical behaviour. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. For “excel forecast linear”, keep the input cells and the result visible while you check the formula in Excel. Follow the worked example and change one input at a time. The steps explain the workbook calculation; this page does not run a live calculator for that task.
Common mistakes
- Predicting far outside the range of the historical x values, where the fitted line carries no evidence.
- Using the linear form on a seasonal series; FORECAST.ETS exists for that and needs evenly spaced dates.
- Mixing up the argument order — the x to predict comes first, then y values, then x values.
Frequently asked questions
What is the difference between FORECAST and TREND?
FORECAST returns one predicted value; TREND returns a whole array of them, and also supports multiple independent variables.
When should I use FORECAST.ETS?
When the data is a time series with a repeating seasonal pattern and evenly spaced dates. The linear form cannot represent seasonality.
Is FORECAST the same as SLOPE plus INTERCEPT?
Yes — =FORECAST.LINEAR(x,ys,xs) equals =INTERCEPT(ys,xs)+SLOPE(ys,xs)*x exactly.
Other ways people ask this
This is also commonly searched as “linear forecast excel” and “forecast.linear excel”. They describe the identical operation, so you are in the right place no matter how you phrased it.
Why do people search for this in so many different ways?
Because the same task has many names. “linear forecast excel”, “forecast.linear excel” all point at the one operation explained on this page, which is why they all lead here.