Forecast Future Values with TREND

Excel Formulas › Statistics

365 / 2021TREND

TREND extends a linear pattern into the future — project next quarter’s sales from the last few. It fits a best-fit line and returns predicted ys for the xs you give it.

Quick formula: predict y for new x values:
=TREND(known_ys, known_xs, new_xs)
Give it the history (ys and xs) and the future xs; it spills the predicted ys along the trend line.

Functions used (tap for the full reference guide):

TRENDFORECAST

The example

Projecting the next periods.

AB
1PeriodForecast
2522.5
3625.0

The formula

The formula:

=TREND(known_ys, known_xs, new_xs) // linear projection

How it works

How it works:

  1. TREND(known_ys, known_xs, new_xs) fits a line to the history and returns predicted ys for the new xs.
  2. It spills a value for each new x — a whole forecast in one formula.
  3. For a single future point, FORECAST.LINEAR(x, ys, xs) is simpler.
  4. TREND assumes a straight-line pattern — check it fits before trusting the projection.

Seasonality breaks linear trends. For data with seasonal swings, FORECAST.ETS (exponential smoothing) models the pattern far better than a straight line. Use TREND for steady, roughly linear series.

Try it: interactive demo

Live demo

History y values; forecast next 2.

Next two:

Variations

Single point

FORECAST.LINEAR:

=FORECAST.LINEAR(newX, ys, xs)

Seasonal forecast

Exponential smoothing:

=FORECAST.ETS(date, ys, dates)

Growth (exponential)

Curved trend:

=GROWTH(ys, xs, new_xs)

Pitfalls & errors

Linear assumption. TREND fits a straight line; curved or seasonal data needs GROWTH or FORECAST.ETS.

Spill space. Multiple new xs spill the forecast — keep room.

Extrapolation risk. Forecasts far beyond the data are increasingly unreliable.

Practice workbook

📊
Download the free Forecast Future Values with TREND practice workbook
A TREND forecast sheet with the single-point, seasonal, and growth variants, plus 4 challenges with answers. No sign-up required.

Frequently asked questions

How do I forecast future values in Excel?
Use =TREND(known_ys, known_xs, new_xs) to project a linear pattern, or =FORECAST.LINEAR(x, known_ys, known_xs) for a single point.
What if my data is seasonal?
Use FORECAST.ETS, which models seasonality with exponential smoothing — a straight-line TREND will miss the pattern.
How do I forecast exponential growth?
Use =GROWTH(known_ys, known_xs, new_xs), which fits a curve rather than a line.

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Related formulas: Linear forecast · Slope & intercept · YTD run-rate

Function references: TREND · FORECAST