The “Egg Principle” in Project Management

March 14, 2024 · 5 min read

The fundamental principles of the PMI standard are outlined in PMBOK, which is a body of knowledge on project management, written by a vast number of professionals. While it constantly evolves and serves as an excellent reference, it might be quite challenging to get its fundamental principles due to a rather dry and sophisticated language.

In this article, we’ll uncover the first one, the so-called “Egg Principle”.

The Egg Principle Uncovered

Imagine a chicken has laid an egg. The egg is immediately a certain size; its shell does not expand further, despite the chick growing inside. The shell is analogous to the project charter.

The charter is a document that outlines the project's framework at the start: timeframes, costs, resources needed, and the content, very roughly. Thus, the charter is a very concise document with very rigid frameworks that cannot expand.

egg principleWhat's inside the egg? The white and the yolk, but you cannot see any bird yet. As the egg is incubated, its contents start to change. The white and the yolk transform into a future bird. Drawing a parallel with project management, the inside of the yolk represents all the other project plans: the risk register, the project schedule, etc.

Behind Waterfall and Scrum

What do managers fear and avoid? They are very afraid of turning project management into a waterfall approach. 

The waterfall approach involves detailing all plans from the start to the end and then overseeing with a whip to ensure people don't get distracted; if they do, they are disciplined. This control is our task as managers. 

The main problem stems from the definition of a project: its finite nature and high uncertainty. In the waterfall approach, all plans are detailed, but since the task is associated with high uncertainty, our plans need constant changes. Eventually, everything devolves into constantly rewriting plans without a clear purpose.

One way to deal with this is to abandon plans altogether, which is what happens in product approaches like Scrum, designed for software development. We simply acknowledge that we can't estimate our plans accurately but instead go to the customer, who formulates what they want. 

We note it down in a wish list — backlog. Then we prioritize and tell ourselves: “Okay, we'll select some wishes and try to realize them within two weeks, and then show what we've achieved to the customer”. If the customer is satisfied, we proceed to the next set of wishes for another two weeks. If not, we revise and present again, and so on. 

waterfall vs. scrum

This iterative process eventually completes all wishes. Where is the planning here? It's almost nonexistent. But in Scrum, over time, we can prioritize more important tasks over another. After working for some time, we'll understand our capacity for a two-week period and retrospectively estimate the time needed to complete all wishes. The advantage of Scrum is that wishes can be gradually added to the backlog.

Scrum's strength lies in avoiding the problem of variability. Its downside? 

While dealing with the issue of high uncertainty, Scrum does not address the problem of finiteness while customers always wonder: “When will the project be finished, and how much will it cost”? That's why Scrum is a good product approach, not a project. So, if you have deadlines, think carefully before using it.

The “Egg Principle” Explained

On one pole is the waterfall approach, and on the other is Scrum. But if we face both high uncertainty and finiteness, what do we do? We manage projects following the “egg principle” discussed earlier. 

This principle attempts to address both challenges — finiteness and uncertainty. 

The customer asks for deadlines and budget. The manager says: “OK, we'll give you a ceiling we won't exceed”. At this moment, the project charter is made. The customer is reassured. Then, the team estimates plans for themselves, not in a waterfall manner but in large blocks. 

They then decompose the nearest weeks and months of work in detail to understand what to do. The plan remains very high-level. When the first phase of work is completed, they proceed similarly with the second phase. This approach is called the rolling wave planning method.

This is an optimal solution. Facing high uncertainty without detailing plans allows us to save time and effort without having to rewrite everything. Yet, we have plans and understanding thanks to the high-level plan, and we see deadlines. 

We can tell if the chick is outgrowing the shell or if there's still room. Here, we can manage the project, rather than just watch what happens as in Scrum. Actually, this is why there's no project manager position in Scrum because no one is responsible for the result within deadlines as there are no deadlines. The whole team is responsible for the sprint's outcome.

The project manager's job is to ensure the chick does not outgrow the shell.

Another important principle is that the shell cannot be tampered with from the inside: the internal plans must not outgrow the charter, nor from the outside. 

If a person who launches the project interferes, changing deadlines, content, cost, the project undergoes significant changes. In this case, the project must be fundamentally relaunched.


Navigating the complexities of project management requires a balance between rigidity and flexibility, as illustrated by the “Egg Principle”. This principle offers a way to manage projects by combining the structure provided by the project charter with the adaptability of agile methodologies like Scrum. 

The key takeaway is that successful project management lies in the ability to adapt, plan, and execute within the constraints provided, ensuring that the “chick” grows but never outgrows the “shell”.

🔎 Read our next article in this series: "The Principles of the Python and of Teamwork and Proactivity"

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