What it is:

Internal rate of return (IRR) is the interest rate at which the net present value of all the cash flows (both positive and negative) from a project or investment equal zero.

Internal rate of return is used to evaluate the attractiveness of a project or investment. If the IRR of a new project exceeds a company’s required rate of return, that project is desirable. If IRR falls below the required rate of return, the project should be rejected.

How it works/Example:

The formula for IRR is:

where P₀. P₁. P_n equals the cash flows in periods 1, 2. n, respectively; and

IRR equals the project’s internal rate of return .

Let’s look at an example to illustrate how to use IRR.

Assume Company XYZ must decide whether to purchase a piece of factory equipment for $300,000. The equipment would only last three years, but it is expected to generate $150,000 of additional annual profit during those years. Company XYZ also thinks it can sell the equipment for scrap afterward for about $10,000. Using IRR, Company XYZ can determine whether the equipment purchase is a better use of its cash than its other investment options, which should return about 10%.

Here is how the IRR equation looks in this scenario:

0 = -$300,000 + ($150,000)/(1+.2431) + ($150,000)/(1+.2431) ₂ + ($150,000)/(1+.2431) 3 + $10,000/(1+.2431) 4

The investment ‘s IRR is 24.31%, which is the rate that makes the present value of the investment’s cash flows equal to zero. From a purely financial standpoint, Company XYZ should purchase the equipment since this generates a 24.31% return for the Company —much higher than the 10% return available from other investments.

A general rule of thumb is that the IRR value cannot be derived analytically. Instead, IRR must be found by using mathematical trial-and-error to derive the appropriate rate. However, most business calculators and spreadsheet programs will automatically perform this function.

IRR can also be used to calculate expected returns on stocks or investments. including the yield to maturity on bonds .  IRR calculates the yield on an investment and is thus different than net present value (NPV) value of an investment.

Why it Matters:

IRR allows managers to rank projects by their overall rates of return rather than their net present values, and the investment with the highest IRR is usually preferred.  Ease of comparison makes IRR attractive, but there are limits to its usefulness. For example, IRR works only for investments that have an initial cash outflow (the purchase of the investment ) followed by one or more cash inflows.

Also, IRR does not measure the absolute size of the investment or the return. This means that IRR can favor investments with high rates of return even if the dollar amount of the return is very small. For example, a $1 investment returning $3 will have a higher IRR than a $1 million investment returning $2 million. Another short-coming is that IRR can’t be used if the investment generates interim cash flows. Finally, IRR does not consider cost of capital and can’t compare projects with different durations.

IRR is best-suited for analyzing venture capital and private equity investments, which typically entail multiple cash investments over the life of the business, and a single cash outflow at the end via IPO or sale .