Reported tester:developer ratios range from 10:1 to 1:10.

Jeremy L. Mordkoff writes:
> There's no simple answer. It depends on so many things, I can't even
> list them all.  Amount of reused code, number and type of interfaces,
> platform, quality goals, etc.
>
> It also can depend on the development model.  The more specs, the less
> testers.  The roles can play a big part also.  Does QA own beta?
> Do you include process auditors or planning activities?

Boris Beizer adds:
> These figures can all vary very widely depending on how you define
> "tester" and "developer".  In some organizations, a "tester" is anyone
> who happens to be testing software at the time -- such as their own.  In
> other organizations, a "tester" is only a member of an independent test
> group.
>
> It is far, far, better to ask about the test labor content than it is
> to ask about the tester/developer ratio.  The test labor content, across
> most applications is generally accepted as 50%, when people do honest
> accounting.  For life-critical software, this can go up to 80%.