Financial calculators include the IRR calculation -- but for a limited number of cash flow events. A spreadsheet will calculate the percentage for any number of future, uneven or even cash flows.

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.

3. Excel’s MIRR function. Excel’s MIRR function (modified internal rate of return) works similarly to the IRR function, except that it also considers the cost of borrowing the initial investment funds ...