# Iron Triangle

The classic project constraints of time, budget, and scope — on time, on budget, to scope.

The iron triangle is the classic model of project constraints: time, budget, and scope, often stated as delivering "on time, on budget, to scope." The three are interdependent — tightening one typically forces a trade against the others — and together they define what project management has traditionally counted as success.

The limitation of the iron triangle is that it measures delivery, not value. A program can hit every constraint — on time, on budget, fully in scope — and still produce no benefit, because none of the three dimensions asks whether the delivered output is adopted or whether it moves the number it was meant to move.

### Commonly confused

Success. A program can satisfy all three constraints and still deliver no benefit; the iron triangle measures delivery, not value.

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