It is difficult to calculate these values manually and while calculators make it easier, Excel is the preferred tool for finding these values over a range of cells.

How to Calculate a Trimmed Mean in Excel. A trimmed mean is much like a standard mean, which you can derive in Excel using the AVERAGE function. However, instead of using all of the data points to ...

Add together all the cash flows you have put in the spreadsheet to calculate a total. Divide the total by the number of historical entries to calculate the mean average cash flow.