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FORECASTING
Seasonal Index Calculator
Calculate monthly or quarterly seasonality indices from historical sales data to forecast future demand.
LIVE PREVIEW
| Month | Year 1 Sales | Year 2 Sales | Average Sales | Yearly Avg | Seasonal Index |
|---|---|---|---|---|---|
| January | 1000 | 1100 | 1050 | 1200 | 0.88 (Low Season) |
| December | 2000 | 2200 | 2100 | 1200 | 1.75 (Peak Season) |
| -- | -- | -- | -- | -- | -- |
| -- | -- | -- | -- | -- | -- |
Instructions
- 1Gather Data: Get at least 2 years of history.
- 2Calculate Average: Find the average sales for each month.
- 3Compute Index: Monthly Avg / Total Yearly Avg. >1 is Peak, <1 is Off-Peak.
Pro Tip
You can import the downloaded CSV directly into Google Sheets, Excel, or Airtable. The formatting is universal.
About this Template
Quantify your business cycles. Know exactly how much to adjust inventory and price for Q4 vs Q1.
Key Features
Index Formulas: Auto-calculate seasonality.
Forecasting: Apply index to future goals.
Common Use Cases
Retail: Holiday planning.
Travel: Peak season rates.
Frequently Asked Questions
Minimum data needed?
24 months (2 full cycles).