Internal Rate of Return (IRR) Explained

Would you put $1,000 into a project that pays back $300, $400, and $500 over three years? The internal rate of return gives that deal a single yearly rate: 8.90 percent. Compare that rate to what your money costs, and the decision gets much clearer. This guide shows what IRR means, how it is found, and where it can fool you.

IRR Quick Reference Table

The table below shows IRR for a few simple cash flow patterns. Each project costs $1,000 today and pays money back at the end of each year. Year 0 is today, so its cash flow is negative.

Notice a pattern in the table. Every project with an IRR below 10 percent has a negative NPV at 10 percent. Every project with an IRR above 10 percent has a positive one. That link is the heart of IRR.

Look at the first two rows as well. Both projects return $1,200 in total. The second one pays more money sooner, so its IRR is higher. Timing matters, not just the total.

What Does IRR Actually Measure?

IRR measures the yearly rate of return built into a set of cash flows. It is the discount rate that sets the present value of money coming in equal to the money going out. At that rate, net present value equals zero.

Think of IRR as a break-even interest rate. Suppose your money costs 7 percent a year to borrow. A project with an IRR of 8.90 percent earns more than that cost. A project with an IRR of 6 percent earns less, so it destroys value.

The word “internal” means the rate comes only from the project’s own cash flows. You do not need a market rate to calculate it. You only need a market rate to judge it.

Key Terms to Know

Cash flow

Money moving in or out in a given year. Money out is negative, and money in is positive.

Discount rate

The yearly rate used to shrink future dollars into today’s dollars.

Net present value (NPV)

The sum of all cash flows after each one is discounted back to today.

Hurdle rate

The minimum return you require, often your cost of capital. A project must clear it.

NPV profile

A graph of NPV at many different discount rates. It crosses zero at the IRR.

How Do You Find IRR by Trial and Error?

You guess a rate, compute NPV, and adjust until NPV hits zero. There is no algebra shortcut for most projects with three or more years. So calculators and spreadsheets repeat guesses very quickly.

Here is how the search works for the project that pays $300, $400, and $500. The NPV at each guessed rate tells you which way to move next.

Each step cuts the gap in half or better. Doing this by hand takes patience, so most people let software handle it. The IRR calculator for uneven cash flows runs the whole search from your list of yearly amounts.

How Does IRR Relate to NPV and ROI?

IRR and NPV use the same math, but they answer different questions. NPV gives a dollar amount at your chosen rate. IRR gives the rate where that dollar amount becomes zero.

Take the project that pays $400 a year for three years. Its IRR is 9.70 percent. At a 10 percent hurdle, its NPV is -5.26, because 10 percent sits above the IRR. At 8 percent, its NPV is +30.84. For the full logic of discounting, read our guide on how net present value works.

Simple ROI is different again. It divides total profit by cost and ignores timing. Both $1,000 projects in the reference table earn a 20 percent ROI, yet their IRRs differ. Our guide on calculating return on investment covers that simpler measure.

When Can IRR Mislead You?

IRR misleads in three common cases: cash flows that flip sign more than once, projects of very different sizes, and unrealistic reinvestment rates. Each one is a well-known limit in finance textbooks.

More Than One Answer

A normal project has one negative cash flow followed by positive ones. That pattern gives one IRR. Some projects end with a big cost, such as cleanup or demolition. Take -100, then +230, then -132. Its NPV is zero at both 10 percent and 20 percent, so it has two IRRs.

Size Blindness

IRR is a percentage, so it ignores how many dollars are at stake. A $100 project returning $150 has a 50 percent IRR. A $1,000 project returning $1,300 has only 30 percent. Yet at 10 percent, the bigger project adds $181.82 of value versus $36.36.

The Reinvestment Assumption

IRR quietly assumes each payment you receive is reinvested at the IRR itself. A 50 percent IRR assumes you can find more 50 percent deals. That is rarely realistic, so high IRRs often overstate true returns.

How Should You Use IRR in a Real Decision?

Use IRR as a quick screen, then confirm with NPV. A U.S. federal guide on cost analysis says IRR alone is not generally an acceptable decision rule. It adds that IRR still gives useful information, especially under tight budgets.

A short routine keeps you safe. First, list every cash flow by year, including end costs. Second, count the sign changes. More than one change means you should rely on NPV. Third, compare IRR to your hurdle rate.

Finally, rank rival projects by NPV, not by IRR. Size and timing can flip the ranking, as the bar chart shows. Where reinvestment worries you, try the modified IRR, or MIRR. It compounds payments at your cost of capital and always gives one answer.

For the $300, $400, $500 project, MIRR at an 8 percent reinvestment rate is 8.63 percent. That is a little below the 8.90 percent IRR. The gap shows how much the reinvestment assumption was lifting the result.

Questions People Ask About IRR

Where These Numbers Come From

This article is general finance education, not investment advice. Worked examples use simple year-end cash flows and were checked by calculation. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated September 27, 2026.