FORECAST
Predicts a future value along a linear trend using existing data points. Uses linear regression to calculate the prediction.
FORECAST(x, known_y's, known_x's)Arguments
xThe data point for which you want to predict a valueknown_y'sThe dependent (observed) data rangeknown_x'sThe independent data range
=FORECAST(13, B2:B12, A2:A12)Predicts the Y value for X=13 based on the existing trend
=FORECAST(2025, Revenue, Years)Projects revenue for 2025 using named ranges
- •Only works for linear trends (straight line predictions)
- •In Excel 365, consider FORECAST.LINEAR or FORECAST.ETS for time series
- •Known_x and known_y ranges must be the same size
- •Using FORECAST on data with a clearly non-linear pattern, like exponential growth or seasonal cycles - it only fits a straight line, so the prediction can be badly wrong for curved trends
- •Mismatching the size of known_y's and known_x's ranges, which raises a #N/A error since every y value needs a corresponding x value
- •Using the legacy FORECAST function without realizing FORECAST.LINEAR is the modern equivalent, or that FORECAST.ETS handles seasonal time series far better than either
FORECAST.LINEARThe modern replacement for FORECAST, functionally identical for straight-line predictions.TRENDCan return an entire array of predicted values along a linear trend, rather than FORECAST's single-point prediction.CORRELMeasures how strongly two variables are linearly related, useful for judging whether a FORECAST prediction is even meaningful.Why does FORECAST give a wildly inaccurate prediction?
FORECAST only fits a straight line to the data. If your underlying trend is curved, seasonal, or exponential, a linear prediction can be badly off - check CORREL first to see how linear the relationship actually is.
Why does FORECAST return a #N/A error?
The known_y's and known_x's ranges probably don't have the same number of data points - every observed y value needs a matching x value.
Should I use FORECAST or FORECAST.LINEAR?
FORECAST.LINEAR is the modern equivalent with identical behavior - FORECAST is kept mainly for compatibility with older files.
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