The Iron Triangle
About this app
Scope, time and cost as an elastic triangle: pull a corner, set pins and test customer requests as change requests. If nothing gives way, quality shrinks.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
The triangle of scope, time and cost
The iron triangle, with quality at its centre, describes the trade-off in every project: scope, deadline and cost depend on each other. Changing one quantity forces at least one other to give way. If the project holds all three fixed, quality remains as the only valve. The triangle is a thinking model. Meeting deadline, budget and scope does not yet prove success, because the project must also create benefit.
What the app shows
In the case project Lumen (fictional) the plan is 40 functions, 28 weeks and €1.2 m. The app shows a triangle whose corners are scope, time and cost, with quality at the core and the approved plan as a dashed outline. The open model derives person-weeks from budget and material costs, and from them team size and feasible scope. Five customer requests appear as change requests with effects and options for the sponsor. Each corner can be fixed with a pin.
Things to try
Pick a customer request such as "finish earlier" and compare the three options: more budget, a later deadline or less scope. Then drag the scope yourself and watch how the free corners compensate. Pin two corners and change the third: only the remaining corner can give way. Pin all three and see how quality shrinks in the middle while the estimation uncertainty is added.
Frequently asked questions
- What is the iron triangle in project management?
- It shows the dependency between scope, time and cost. Changing one quantity affects at least one other. Quality is often added at the centre, and it suffers when none of the three may give way.
- Why can a project not be faster, cheaper and better at once?
- More scope in less time needs more staff, which costs money and adds coordination effort. With budget and deadline fixed, a larger scope is only possible at lower quality. Without room in one corner a gap appears.
- How should project management handle change requests?
- It assesses the effect on scope, time and cost and presents options to the sponsor. The sponsor decides which corner gives way. It helps to clarify at the start which corner is negotiable.
- What does the model in the app calculate?
- Person-weeks follow from the budget minus €360,000 material costs at €5,000 per person-week. Feasible scope follows a square-root function, because large teams deliver less per head. The rates are assumptions for the case, not measurements.
Subject: Projektmanagement
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