Internal rate of return (IRR) is the interest rate where the net present value of all cash flows from a project equal zero. IRR can be used to compare projects, with higher IRR projects considered more profitable. IRR is calculated using the formula where present values of future cash flows are set equal to the initial investment and solved for the discount rate. An example shows a company calculating the 24.31% IRR of equipment purchase by setting the net present value equal to zero.