Definition of ROI – Return on Investment


We talk about ROI all the time – what is it, in layman’s terms?

ROI is the acronym for return on investment. Another way to think of it is “How much profit will we make if we invest in this project?” Profit is revenue minus costs. Technically, the question should be “How much profit will we make, relative to our investment, if we invest in this project?” We’ll look at both definitions, and see the differences below.

Note – we also have posts explaining expected value and net present value (NPV). Both of these should be incorporated into any real-world ROI calculations, but the examples in this post do not include them, for the purpose of making ROI easier to understand.

A very simple example

We will imagine a software project to build a website for our company. The website takes 4 months to develop, plus we will need some developers to fix bugs for the first month after the site goes live. So, we will be spending money for 5 months. We’ll also assume that we already have the server and network access, so there are no extra costs associated with running this project (other than the developer salaries). We have a plan to get the software delivered as quickly as possible, so once we get the project running, we will double the size of our staff (in the third month of development). In the last month of development, we will increase our costs by another 50% because we have a real-world project, and we discover that we’re going to miss our deadline if we don’t increase staff (or pay for some overtime).

Here’s what our costs per month look like.

[Ed: 86% of you can assume the costs are measured in thousands of USD. 10% of you should assume your local dollars, 3% should use british pounds, the rest of you can use euros, yen, krona (Swedish and Icelandic), rupee, shekels, dirham, won, rubles, baht or pesos. That covers the top 20 currencies for our readers as of this writing.]

cost data chart

We also see that the total cost of the project is projected to be 80. So our investment is 80.

Cost is only half of it – what about revenue?

In our setup, we identified that the website will go live after four months, and will start generating revenue in month 5. Also, since we measure things in internet time, we will assume that we are only projecting revenue for the next twelve months. Twelve months from now, we have no idea if someone will compete with us with a better, free, open-source solution, or if we’ll keep making money. So we’ve decided to only look at revenue that happens between now and twelve months from now. If we add that projected revenue to our cost data, we get this:

cost and revenue data chart

It’s now very clear that we will spend 80 units to get 230 units back. Our profit is 230-80=150. So we get almost twice what we invest back. The answer to our first question (How much will we make if we invest in this project?) is 150.

ROI – Return on investment

The ROI, or return on the investment is 150. To determine the relative earnings, we simply need to divide net revenue by the amount that we invested. 150/80 = 1.875, or 187.5% This answers our second question (How much will we make, relative to our investment, if we invest in this project?) is 187.5%.

The ROI for this project is 187.5%. Sounds like a really good project.

19 thoughts on “Definition of ROI – Return on Investment

  1. Great post!

    Comparing ROI between projects (or potential releases items) is an excellent way to prioritize development activities. One thing that you must be careful with is the timing of the cashflows. The more distant they are, the less they will be worth in terms of today’s dollars (e.g., I’ll give you $100 3 years from now if you give me $100 today. Somehow I don’t think anyone will accept.) In your example, this is not an issue because everything occurs within the same year.

    If you do not use Net Present Value (NPV) you may choose a project that has a higher absolute dollar return but is actually worth less in terms of current dollars. Generally, some discount factor is applied to future cashflows which accounts for inflation, the cost of borrowing and some additional percentage points (opportunity cost). The NPV formula will account for the compounding affect. You can read up on NPV @

  2. Thanks Marcus!

    Yes, I absolutely want to get into NPV, IRR and hurdle rates, payback period and other measures. There’s a bunch of this stuff to cover, just starting with the basics for now. Thanks for the wikipedia link too.

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