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IRR Calculator

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Thumbnail image of Alastair Hazell By Alastair Hazell. Reviewed by Chris Hindle.

Cash flows

Use this calculator to calculate the internal rate of return (IRR) and measure the profitability of an investment. You can choose to enter yearly cash flows or simply calculate based upon a multiple.

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Table of contents:

What is IRR?

IRR stands for the internal rate of return. The IRR is an interest rate which helps you compare the profitability of different investments or projects, providing an estimate of the rate of return expected from each.

In technical terms, IRR can be defined as the interest rate that makes the Net Present Value (NPV) of all cash flows from the investment equal to zero.

Say you own a restaurant, and you consider getting a bank loan to develop a larger dining area; you need to know whether this investment is worthwhile or if it will cost more than it gains. If the loan costs 10% and the IRR is 20%, it is a worthwhile investment. If the loan costs 10% and the IRR is 9%, it’s an unwise investment.

IRR differentiates between money at different points in time, on the basis that receiving money now is more useful than receiving it in the future. So if all factors are equal when calculating the restaurant development’s potential, the IRR would be higher if the restaurant remodelling is finished in peak season (more money in now), than in quiet season (more money later).

And in short, a larger IRR is a good thing for business - the higher the IRR, the better the return of an investment. 1

How to calculate IRR

Unlike most math problems, where a fixed formula would usually lead us neatly to the result, finding the IRR is not so simple. It’s like shopping for a suit without measurements. We have to use trial and error to experiment with different figures, testing out different percentages in the IRR’s place to see how they fit.

Given this slightly cumbersome process, it makes life much easier to use our online calculator (found at the top of the page). We know when we’ve landed on the correct IRR, as it’s the one which sets the the net present value to zero.

Oh… But what is the net present value?

What is the net present value?

Net present value (NPV) measures the expected profitability of a project or investment by calculating the difference between the present value of cash inflows and the present value of cash outflows over a period of time.

NPV is a measure of cash flow.
  • Net = after deductions
  • Present = current, right this moment
  • Value = the worth of something

So if a net present value is a minus number, you’re losing money on that project/investment. If it’s a positive number, you’re making money on the project/investment.

To work out the net present value, add together the present values of all money coming in, and subtract all present values of money going out. So basically, deduct expenses from income. (Present values just means the worth of the money today, not when it’s potentially gained interest a year from now.)

Calculation example

Lily bought a jug ($10), some lemons ($10), some sugar ($1), and rented a kiosk for the day ($4). The present values of all her outgoings came to $25.

She then sold 40 cups of lemonade for a dollar each, so the present value of the money in came to $40.

The net present value of her business venture can be calculated by deducting her expenses from her income.

Net present value = 40 - 25 = 15

So Lily’s lemonade stand has a net present value of $15.

Now we need to experiment with interest rates until the net present value becomes 0.

If we were calculating this manually, we could try entering a 50% rate in our spreadsheet, but that would give us a positive number. So we would jump higher, and see that a 70% rate gives us a negative number. So we would try something in the middle, until the NPV comes out at 0, neither positive nor negative. We would then find that Lily’s lemonade stand has a 60% IRR (or 60.01% to be extra precise).

Lily can now go on to work out her profit margin, as another important metric for her burgeoning lemonade business.

What is the difference between IRR and ROI?

Businesses often talk about their ‘return on investment’ (ROI), which is a useful figure to see how successfully profits outweigh expenses. However, the ROI uses fixed values and doesn’t consider how money changes over time. An investment of $100 in 1976 which returns $200 in 2020 is obviously not such a successful investment as an investment of $100 in 1976 which returns $200 in 1977.

Therefore, IRR is more useful for long-term investments. As with all business investment analysis it makes sense to look at a combination of metrics that are relevant to that business and sector, to get a fuller picture, rather than looking at one measurement in isolation.


As we mentioned above, when analyzing an investment's performance over time, you may wish to bring in other metrics to get a more nuanced view of your investment performance. These include measures such as NPV (discussed earlier) and CAGR (compound annual growth rate).

CAGR is a measurement of the mean annual growth rate of an investment over a specified time period. It smoothes out the returns of an investment as if it had grown at a steady rate on an annually compounded basis.

By considering metrics such as IRR, CAGR and NPV in combination, you can grasp the potential total return (IRR), the expected annual growth (CAGR) and the profitability of an investment in terms of present value of future cash inflows and outflows (NPV). This gives you a more comprehensive evaluation of your investment's performance and potential.

If you're interested in learning more about combining metrics for investment analysis, you may wish to read the article 'A Refresher on Internal Rate of Return' by Amy Gallo. It features a discussion about IRR and NPV with Joe Knight, bestselling author of "Financial Intelligence" and co-founder of the Business Literacy Institute.

I hope you found this IRR calculator and article useful. As we always say, when it comes to investing, you may wish to consult a professional financial advisor before making any major investment decisions.

Before you go...

Why not check out our range of other financial calculators in our finance section?


  1. Internal Rate of Return (IRR) Rule: Definition and Example, Investopedia.

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