The modified internal rate of return (MIRR) is a financial measure of an investment's attractiveness.
[3] This is usually an unrealistic scenario and a more likely situation is that the funds will be reinvested at a rate closer to the firm's cost of capital.
Generally for comparing projects more fairly, the weighted average cost of capital should be used for reinvesting the interim cash flows.
Secondly, more than one IRR can be found for projects with alternating positive and negative cash flows, which leads to confusion and ambiguity.
Spreadsheet applications, such as Microsoft Excel, have inbuilt functions to calculate the MIRR.