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Demand Planning & Forecasting lesson

Seasonal index

A seasonal index compares each quarter with the average quarter. Last year averaged 300 units a quarter.

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About 5–10 minutes · no sign-up needed

The idea

A seasonal index compares each quarter with the average quarter. Last year averaged 300 units a quarter:

Formulas

Sales ÷ 300

Key points

Seasonal indexQuarter sales ÷ Average quarter sales.
Above 1A busier than average quarter.
Below 1A quieter than average quarter.

Seasonal indexes turn a flat forecast into one with the right peaks and dips.

Practice

Try each one in your head first, then open the answer.

1. In C5, work out Q4's seasonal index: Q4 sales ÷ the average of all four quarters.
=B5/AVERAGE(B2:B5)
2. What's Q3's seasonal index? Round to two decimal places.
250 ÷ 300 = 0.83
3. Tap the quarter that sells exactly an average amount.
Q2: 300 units, an index of 1.0.

Learn it by doing. This lesson is a short hands-on level on Bampaa: see it work, then build and write it yourself, with instant feedback.

Try this lesson free →
About 5–10 minutes · no sign-up needed