The Excel FORECAST.LINEAR function predicts a future value along the straight line of best fit through known x–y data — the modern replacement for the legacy FORECAST function.
Syntax
| Argument | Description | |
|---|---|---|
x | Required | The data point (x value) at which you want a prediction. |
known_ys | Required | The known dependent values — the y's you are predicting. |
known_xs | Required | The known independent values — the matching x's. Must be the same size as known_ys. |
How to use it
FORECAST.LINEAR fits a least-squares regression line to your known points, then reads the y value on that line at the x you give. The order of arguments is the y's before the x's:
It is mathematically identical to INTERCEPT + SLOPE * x — the line's intercept plus its slope times your x. The x can lie outside the known range (extrapolation) or inside it (interpolation).
FORECAST vs FORECAST.LINEAR: they return the exact same number. FORECAST.LINEAR (Excel 2016+) is the renamed, future-proof version; the old FORECAST still works for backward compatibility but Microsoft recommends the new name.
For data with a repeating seasonal pattern over time, reach for FORECAST.ETS instead — it models seasonality, which a straight line cannot.
Try it: interactive demo
Pick a FORECAST.LINEAR example to see the formula and its result.
Practice workbook
Frequently asked questions
Is FORECAST.LINEAR the same as FORECAST?
FORECAST.LINEAR was introduced in Excel 2016 as the future-proof name; the original FORECAST remains only for backward compatibility.What is the argument order?
(x, known_ys, known_xs) — the value to predict first, then the y's, then the x's. Mixing up the y and x ranges is the most common mistake and gives a wrong result.Can I forecast beyond my data range?
When should I use FORECAST.ETS instead?
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