Tester versus Developer ratio

My manager asked about Test to Developer ratios and I stated the industry “norm” was 1:3.   He asked for backup of that statement and thus I did an internet hunt and found the information below.   While I agree with those that say the ratio is meaningless outside lots of context and history, management always asks for it anyways (like block code coverage).   My experience at Microsoft has been with ratios around 1:1 (+/- .5).  Couldn’t find the quote I recall from Bill Gates saying he feels at times like he is running a testing company instead of a development company because we have so much testing.  My prior companies were very close to 1:3. 


References for dev/test ratio:


Took a while, but I found the one I remembered:


The Elusive Tester to Developer Ratio


“The above chart shows that the ratio of 1 tester to 3 developers was the most common ratio reported.”

2016 Update:  See also http://rube.asq.org/software-quality/2016/03/benchmarking/the-elusive-tester-to-developer-ratio.pdf  also by RANDALL W. RICE
“Most Recent 3rd Survey was a small survey of 22 companies worldwide, 19 of which were able to provide accurate information about their tester-to-developer ratio. The findings were:

  1. The range of ratios was much tighter.  The range was one tester to one developer on the richer end of the scale, to one tester to seven developers on the leaner end.  This may be due to the small sample size.
  2. The majority of responses (16) were just 3 ratios: 1 tester to 1 developer on the low side, and 1 tester to 3 developers on the high side.  
  3. The average and most common ratio was 1 tester to 2 developers. “

All you need to read fromManage and Strengthen Testing


“Add test resources. Many test efforts today are under-resourced, partly because of optimism, denial, and lack of understanding of what is needed to perform an adequate test. Many managers and professionals are surprised by the amount of testing indicated by time-proven test estimating formulae, and frankly do not believe them. However, we have considerable evidence that these rules of thumb are about right, from actual projects in leading software organizations. Many software vendors, for example, have a ratio of software engineers to testers of 3:1 or 2:1.”



Sizing the QA Group – Theory and Application slide 32  [I love Proprietary & Confidential marked material on the public internet]


“Some examples of developer to tester ratios:

Space shuttle project = 1:3

Large statistical software company = 1:1

Huge software conglomerate = 1:1

Healthcare IT firm = 4:1

Analytical CRM company = 4:1

Technology consulting firm = 8:1

These are based on mostly anecdotal data

Very few companies will publish this

Except those who can afford 1:1 ratio”


Actually I recall data (too lazy to find it) showing space shuttle onboard, life critical software, with 1 dev to 7 testers (1:7) ratio. 

Other articles

Moving Constraints   [David J. Anderson MS PM   J]
            “with a very high quality development team, you may need a 1:1 ratio of testers to developers.”


It Depends: Deciding on the Correct Ratio of Developers to Testers

http://www.jrothman.com/Papers/ItDepends.html  — I like this article as it builds suspense to end – how did the quality turn out given the factors?


Estimating Tester/Developer Ratios (or Not).
http://www.kiberle.com/pnsqc1/estimate.doc  Couple good examples and a model (shows why dev leaving unit test to test doesn’t work)


Can probably skip:


PNSQC 2001 [7.45 MB]   Just deplores ratios: 

Ratios out of context are meaningless. Attempting to use industry figures for ratios is at best meaningless and more likely dangerous.”



A diversion you might like:

A Fable about Developer/Tester Relationships: Does trying to get developers to test their code feel like trying to get your children to clean their rooms?

Reflections on a Fable about Developer/Tester Relationships responses to your feedback, along with a few insights about the dynamics behind developers examining their work.


About testmuse

Software Test Architect in distributed computing.
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