Glossary · IT & systems
Boehm's law
Boehm's law says that an error becomes more expensive the later you discover and fix it, and that the cost rises exponentially.
Boehm's law is a rule of thumb from software development, named after the engineer Barry Boehm, who backed it up with figures in the late 1970s. The core idea is simple: the later in a project you discover and fix an error, the more it costs. And that cost does not rise in proportion, but exponentially.
Why the cost rises so quickly
The classic illustration is the ratio of 1 to 10 to 100. A wrong assumption that you correct while you are still planning costs almost nothing. The same error that only comes to light during testing costs many times more, because work already depends on it by then. And if it only turns up in production, with real users, the bill runs up to a hundred times as much: the fix, the explaining, the lost trust and the work you have to redo.
What it means for you
The lesson is not that you should avoid errors, because that will not work anyway. The lesson is that you want to find them early. Testing an assumption before you set it in code, scrutinising a choice before the supplier starts building: it feels slow, but that is exactly where you save the most money and time. It is also why an honest interim check often pays for itself.
