Internal Rate of Return (IRR) Basics
How do you summarize into a single number the return of an investment where you put money in many times and take it out many times? That answer is the internal rate of return (IRR).
What is IRR
The Internal Rate of Return (IRR) is the discount rate that makes an investment's net present value (NPV) zero. Put a bit more plainly, it's 'the interest rate at which the present value of the money coming in exactly equals the present value of the money going out.'
For example, if you put in about $7,400 today and get back about $8,140 one year later, the discount rate that makes this cash flow balance exactly is 10%. That is, IRR = 10%. It means this investment 'produces the same result as a deposit earning 10% per year.'
Why 'make NPV zero'
NPV (net present value) is the value obtained by pulling all the money you'll receive in the future to present value, summing it, and then subtracting the money you put in today. Raising the discount rate makes the present value of future money smaller; lowering it makes it larger.
The discount rate at the point where NPV becomes zero is exactly that investment's 'inherent return.' This equation can't be solved neatly by hand, so a computer finds it by trying various values (iterative calculation).
You can understand IRR as a metric that asks back, 'what is the uniform annual compound interest rate that produces this investment's result?'
The relationship between IRR and XIRR
Basic IRR assumes cash flows occur at 'even intervals (e.g., the end of each year).' But real recurring investing has irregular dates.
XIRR is an IRR calculated as an annual rate that reflects the 'exact date' of each cash flow. When cash flows are regular, IRR and XIRR produce the same value; when irregular, XIRR is more accurate. That's why XIRR is used for actual investment performance calculation.
IRR's traps
IRR is powerful, but blind trust is forbidden. When the sign of cash flows changes multiple times (repeatedly putting in and taking out), IRR can come out multiple or fail to calculate.
Also, IRR implicitly assumes 'money received in the interim is reinvested at the same IRR.' In reality you may put that money to work elsewhere at a lower rate, so there's room for IRR to appear higher than the actual return you experience.
Frequently Asked Questions
Q. How does IRR differ from CAGR?
CAGR is the annual compound return of a single 'put in once, take out once' investment. IRR summarizes complex cash flows of putting in and taking out multiple times into a single annual rate. When there are only two cash flows—the start and end—IRR and CAGR come out to the same value.
Q. Are there cases where IRR can't be calculated?
Yes. When the direction (sign) of cash flows changes often, or in extreme profit-and-loss structures, the equation may have multiple solutions or fail to converge. In such cases the calculator displays 'cannot calculate' or shows one of several IRRs.
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📋 Results are based on historical data; past returns do not guarantee future returns.
📋 This service is provided for educational purposes to help you understand investing, not as investment advice.