# Seasonal Indices for Quarterly Data

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

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 number of periods (i.e. years) multiplied by 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 average for each season over periods, i.e. sum data for first quarter and divide by number of years, and repeat this to each quarter.
- Calculate seasonal index for each season by dividing seasonal average by total average and expressing result in percents.

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

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