# Seasonal Indices for Quarterly Data

This online calculator calculates seasonal indices based on quarterly data using the method of simple averages

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This calculator complements Seasonal fluctuations. Seasonal indices. Method of simple averages calculator, which works only on **monthly** data. Here you can enter your **quarterly** data, and the calculator computes **seasonal indices** using the **method of simple averages**. There are several methods to calculate seasonal indices, and the method of simple averages is the simplest of them. Technically, you calculate seasonal indices in three steps.

- Calculate total average, that is, sum all data and divide by the number of periods (i.e., years) multiplied by the number of seasons (i.e., quarters). For example, for three years data, you have to sum all entries and divide by 3(years)*4(quarters)=12.
- Calculate the average for each season over periods, i.e., sum data for the first quarter, divide by the number of years, and repeat this to each quarter.
- Calculate the seasonal index for each season by dividing seasonal average by total average and expressing the result in percents.

The sum of all indices should be 100%*(number of seasons). In case you have lost some precision during the calculation, you may need to normalize your data. For quarters, divide 400% by your sum, then multiply each index by the obtained coefficient. After that, they will add up to 400%.

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