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Internal Rate of Return Formula

The IRR, or the Internal Rate of Return, is a popular method of capital budgeting. The figures that you get when calculating the IRR are essential to determine if you place a long term investment, or if it is better to take your money elsewhere. But what is the formula to find the IRR figures?

You’d say that one needs an economic background in order to obtain the IRR of a possible venture, but this is not strictly the case. As a matter of fact, there is the Internal Rate of Return Formula that can help you disentangle all those figures and see if they look good or not for any potential long term investment.

The formula is not difficult if you know what the initials stand for. The IRR formula is a mathematic procedure that involves the time value of money by taking into account the cash flows over the length of a certain project.

Basically, the Internal Rate of Return Formula goes after the following pattern:


NPV= 0 = I+ CF 1 + CF2 + + CF n (1+IRR)1 (1+IRR) 2 (1+IRR)n

In this rule the NPV initials represent the net present value, which must be zero at all times, as you can see in the formula.

The I stands for the initial investment (the money you start the deal with), and n stands for the total number of years/ months or weeks the project is intended to last.

The CF is the cash flow and the number that stands besides each CF is the year/month of the investment. So, for example, CF1 means the cash flow for the first year of the investment. This formula is made for a number of ‘n’ years. The cash flow of each year or month for the duration of the project is considered as the factual sum of money that the company or firm obtains in a year (month) after having paid all the taxes and expenses of the investment.

The IRR reflects the internal rate of return, or break-even rate of return as some people like to call it. N stands for the number of years or months the investment is intended for. For example, if you want to enter a venture for 5 years, n equals 5. If you want it for 10 months; n equals 10 and so on.

After having applied the formula, you must be able to interpret the results. Compare some figures to some previous successful investment plans. Or if you have more plans, compare the figures and the plan with the highest IRR should be the most profitable, at least in theory. As a result, when investing capital, it is essential to calculate the IRR and compare it to other figures. Also, make sure the IRR is greater than the costs of the investment to ensure profitability overall for the project concerned.

Companies and firms that want to calculate the worthiness of a certain business or venture frequently use the Internal Rate of Return Formula. Knowing the IRR can ensure the success of future investments.


If your not very good at using your HP12C calculator or you don’t have one, the great thing about the KISCL software is that it calculates the IRR for you. Check out this static screen shot showing you just how easy it is to not only calculate your IRR, but how easy it is to change numbers and see many ‘What If’ scenarios. Sample of the Loan Sizer Tool.
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