# Iron Triangle The Iron Triangle, also called the triple constraint or the project management triangle, is a model of the constraints a project works under: scope, time and cost. Quality is often drawn in the middle, because it's what suffers when the three corners get out of balance. The corners are linked. More scope needs more time or more money. A tighter deadline needs more money or less scope. Cutting the budget without touching the deadline or the scope degrades quality. The origins of the model are unclear. One documented early version comes from Martin Barnes, who drew a triangle with cost, time and quality at its corners for a 1969 course called "Time and Cost in Contract Control". The trade-offs aren't always available in practice: adding people to a late project can slow it down further. Roger Atkinson's 1999 critique adds that the triangle measures how well a project was delivered, not whether it succeeded: a project can hit its time, cost and scope targets and still bring no benefit to its users. That's why projects also need [[Success criteria]]. For knowledge workers, time and money are often fixed (a launch date, a few hours per week), which leaves scope as the corner you can actually move. [[Shape Up]] builds a whole method on that: fixed time, variable scope. ## References - https://en.wikipedia.org/wiki/Project_management_triangle - Roger Atkinson, "Project management: cost, time and quality, two best guesses and a phenomenon", International Journal of Project Management, 1999: https://doi.org/10.1016/S0263-7863(98)00069-6 ## Related - [[Scope creep]] - [[Scope hammering]] - [[Success criteria]] - [[Appetite (Shape Up)]] - [[Shape Up]] - [[Minimum Viable Product (MVP)]] - [[Quality vs user satisfaction (Article)]] - [[You can always trade time for features, but you can never trade features for time]] - [[Large projects act as magnets attracting additional cost, scope, and risk]] - [[Project Management Body of Knowledge (PMBOK)]] - [[Project Management (MoC)]]