This tool computes the seasonal index for a given time series. Availability of the seasonal index makes seasonal adjustment in forecasting, and it enables us to deseasonalize time series to reveal if there is any real trend which might have been masked by the seasonality pattern.

Enter your up-to-12 unit period data row-wise. The columns are devoted to monthly, weekly, quarterly, etc. After entering your time series correctly in the matrix, then click the Calculate button. Blank boxes are not included in the calculations but zeros are.

In entering your data to move from cell to cell in the data-matrix use the Tab key but not the arrow or enter keys.

To edit your data, including add/change/delete, you do not have to click on the "clear" button, and re-enter your data all over again. You may simply add a number to any blank cell, change a number to another in the same cell, or delete a number from a cell. After editing, then click the "calculate" button.

For extensive editing or to use the tool for a new set of data, just click the "clear" button.