How much of total software cost goes to maintenance?

September 8, 2009

I thought I had a simple question: How much of total software cost goes to maintenance? I want a number that is recent, backed by evidence, and generally citation-worthy.

It turns out it’s hard to find. Software engineering course notes online tend not to cite their sources. Recent estimates tend to come from magazine articles citing Gartner or Forrester. A 2000 IEEE-published article was cited as “90%,” but digging into the paper I find:

According to an informal industry poll,85 to 90 percent of IS budgets goes to legacy system operation and maintenance.

If you know where I should look, please get in touch.


3 Responses to “How much of total software cost goes to maintenance?”

  1. Jorge Says:

    Well, this is anything but a simple question!

    * Do you mean how much money the software company spends after it releases a version of their code? How much time?

    * What if some of the changes go towards the next release of the software? Does it still count as maintenance?

    * What domain are we talking about? Different domains must have very different approaches to maintenance, with the corresponding impact to their costs.

    * Do you include investments done while developing the software exclusively for the purpose of simplifying maintenance tasks?

    You’ll probably find numbers, but they may well be wrong. In any case, a standard number I’ve seen in Software Engineering textbooks (and, I think, in one of McConnell’s books) puts maintenance roughly at 50% of the total cost of a software system.

  2. Ian Says:

    You might be searching for the wrong thing … a quick google of software life cycle costs turned up a master thesis that might be of interest (sorry … I just searched, didn’t read it!): A second IEEE article looking interesting too:

    There has got to be papers and studies out there … certainly the life cycles costs are affected by how long the release is in the field, etc … and there are falling costs as the software ages, Surely companies that sell life cycle mgmt software and cost claim cost savings from their IDEs etc must have info/studies to back that up …

  3. Joel Stobart Says:

    I just got 3rd hand a post from Microsoft that would be so useful in concert with this post.

    I would really love to know the average percentage cost of a defect to the project post release.


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