2 Surprising Truths About The Iron Triangle

Project management 101 teaches that, when managing outcomes, you cannot alter scope, schedule, or cost (resources) without affecting at least one of the other dimensions. This interrelationship is known colloquially as the “Iron Triangle.” Sometimes we put “quality” in the middle to show how it is unavoidably shaped by choices on the other constraints:

Image credit: John M. Kennedy T (Wikimedia Commons)

Lots of Dilbert cartoons derive their humor from the unwillingness of the Pointy Haired Boss (PHB) to acknowledge this relationship. These cartoons are funny because they are so eerily similar to conversations we’ve all had, where someone wants us to deliver ultra-high quality, on a limited budget, in an aggressive timeframe, with a boatload of features.

It ain’t gonna happen, folks. We engineers are clever, but we’re not magicians. Triangles don’t work that way.

You’ve learned some good principles when you can articulate this geometry lesson.

But there’s more.

Truth 1: Scope is a trickster

Many well meaning managers and executives understand this trilemma, and they distance themselves from Dilbert’s PHB by acknowledging that something has to give. “I pick scope,” they’ll say. “We absolutely must have the product before the summer doldrums, and we only have X dollars to spend, but I’m willing to sacrifice a few features.”

This can give product management heartburn–feature sets sometimes hang together in ways that make slicing and dicing dangerous. An airplane that’s good at takeoffs but that can’t land is unlikely to be a commercial success. Good product managers will point this out, and they’ll be right.

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