Rolling period calculations in Tableau - Real Business Scenario

Scenario Mode

👤 Your Role: You are a sales analyst at a retail company.

📋 Request: Your manager wants to see the 3-month rolling sales totals to understand recent sales trends better.

📊 Data: You have monthly sales data for the past year, including the month and total sales amount.

🎯 Deliverable: Create a Tableau line chart showing monthly sales and a 3-month rolling total sales line to compare trends.

Sample Data

Month	Sales
2023-01	1000
2023-02	1200
2023-03	1100
2023-04	1300
2023-05	1250
2023-06	1400
2023-07	1500
2023-08	1600
2023-09	1550
2023-10	1650
2023-11	1700
2023-12	1800

1

Step 1: Connect your sales data to Tableau and load the data source.

Import the data table with columns 'Month' and 'Sales'.

Expected Result

Data is available in Tableau with 12 rows representing each month.

2

Step 2: Create a calculated field for the 3-month rolling sales total.

WINDOW_SUM(SUM([Sales]), -2, 0)

Expected Result

A new field that sums sales for the current month and previous two months.

3

Step 3: Build a line chart with 'Month' on the Columns shelf and 'Sales' on the Rows shelf.

Drag 'Month' to Columns, drag 'Sales' to Rows.

Expected Result

A line chart showing monthly sales values.

4

Step 4: Add the 3-month rolling sales calculated field to the Rows shelf to overlay on the chart.

Drag the calculated field '3-month Rolling Sales' to Rows next to 'Sales'.

Expected Result

The chart shows two lines: monthly sales and 3-month rolling sales totals.

5

Step 5: Format the chart for clarity: add labels, legend, and title.

Add chart title 'Monthly Sales and 3-Month Rolling Total', enable data labels, and add legend.

Expected Result

Clear, easy-to-read chart comparing monthly sales and rolling totals.

Final Result

Month: 2023-01 to 2023-12

Sales  |      *       *       *       *       *       *       *       *       *       *       *       *
       |     * *     * *     * *     * *     * *     * *     * *     * *     * *     * *     * *     * *
       |    *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *
       +---------------------------------------------------------------------------------------------->
        2023-01 2023-03 2023-06 2023-09 2023-12

Legend:
* Single star line = Monthly Sales
* Double star line = 3-Month Rolling Sales Total

✓The 3-month rolling total smooths out monthly fluctuations and shows clearer sales trends.

✓Sales generally increased over the year with some seasonal dips visible in monthly sales.

✓Rolling totals help identify sustained growth periods better than single month values.

Bonus Challenge

Create a 6-month rolling average sales calculation and add it as a third line on the chart.

Show Hint

Use WINDOW_AVG(SUM([Sales]), -5, 0) as the calculated field for the 6-month rolling average.