FORECAST.ETS.SEASONALITY Function in Excel: Which Cycle Did Excel Find?

⏱ 1 min readUpdated 28 September 2026

StatisticsLevel: ExpertAvailable in: Excel 2016+

In this article
  1. Syntax
  2. Examples
  3. Example 1
  4. Related functions

FORECAST.ETS.SEASONALITY reports the season length Excel detected — 12 for a yearly cycle in monthly data, 7 for a weekly cycle in daily data.

Syntax

=FORECAST.ETS.SEASONALITY(values, timeline, [data_completion], [aggregation])
Argument What it means
timeline Evenly spaced dates.

Examples

Example 1

=FORECAST.ETS.SEASONALITY(B2:B37, A2:A37)

Should return 12 for three years of monthly sales with a festive peak.

FORECAST.ETS

📚 Part of the free Excel course: Beginner → Expert · Try it in the Formula Lab or ask the AI Helper.

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