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. Most people learn this as a sequence of clicks and forget it by next week; learning it as a pattern instead is what lets you apply it to the next, slightly different version of the problem without starting from scratch. That is the difference this page is trying to make. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “cash forecast template excel”. Start on a copy or a tiny sample, keep the affected cells visible, and compare the result with the outcome you expected before you touch the real workbook. 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. The point is a calculation you can defend to a CFO or an auditor, but the practical win is that someone else can open the file and understand what happened without asking you.
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. Keep this page bookmarked for the next time the same question comes up. Better still, repeat the steps once in your own workbook — doing it yourself is what turns a copied answer into something you remember. For “cash forecast template excel”, 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.