The Triangle of Truth

(Quick writers note: Ok, I admit, Ron Baker has shamed me
into finally writing this post. His post on Chris Marston’s excellent blog has
motivated me.)

One of the basic principles of project management is what is
known as the triple constraint. Some call this the scope, resource, time
triangle. However, when I was the practice manager of a software implementation
consulting firm, one of the guys on the team, Dave Franz, dubbed it the
Triangle of Truth. (Franzy, if you are out there, you
should know I give you credit whenever I talk about it.)

The concept is simple. A project consists of three
interrelated variables: scope, resource (some say cost), and time. These
variables are like the angles of a triangle. If you recall from geometry class
in high school, in order for a polygon (shape) to be considered a triangle the
three angles must add to 180 degrees. I.e., Angle A (Scope) + Angle B
(Resource/cost) + Angle C (Time) = 180. If these do not add to 180 you don’t
have a triangle. So, if you make a change to the value of one of the angles,
one of the other two or both must also change to compensate or else the figure
is broken.

The big problem with most professionals is that they are
lousy and lazy about scope development. They prefer to concentrate on the
second two elements, cost and time. In some cases, the professional feels
pressure from the customer or prospect to give answers to the cost and time
questions first. To me this would be the equivalent of purchasing the lumber for
a new house before going to an architect for plans; or doctor writing a
prescription before performing a diagnosis. (Remember: prescription before
diagnosis equals malpractice!)

To refute this poor practice further, I need to reference one
of the giants of the consulting profession, Peter Block.

In his landmark book, The Answer to How is Yes!, Block posits
that consultants (read professionals) are usually presented first with what he
calls “How” questions. “How much will it cost?” and “How long will it take?”
are two of these questions — angles B and C in our triangle. Block argues that
while these are relevant questions, when asked too early, they “express our
bias for what is practical, concrete, and immediately useful. It assumes we
don’t know and this in itself becomes a defense against action.”

Scope (angle A), however, is a “What matters?” or “Yes!”
question according to Block, specifically the question is “What do we want to
create?” In order to properly begin a project with a balanced (or equilateral)
triangle we must ask and fully answer this question first. Why do we need a
balanced triangle?

If we go back to the analogy and take it one step farther, let
us draw a circle inside this triangle, the size of the circle represents the
quality of the work performed. The largest perfect circle can be drawn inside a
triangle that is equilateral, all sides the same and, therefore all angles
equal to 60 degrees.

This is an important point because for a professional
knowledge firm (PKF), quality is defined exclusively by the customer not the
professional. The professional cannot say that they do quality work. Rather,
their customers can say that about them.

What happens in most firms, as Chris so eloquently points
, is that scope is often poorly or not-at-all defined. I am sent an email a
week from someone asking me to assist them with scope creep on a project. My
first response is to ask them to send me a copy of their scope document. In
almost all cases, I am sent back a proposal with a range of hours.

In replying to this I tell the poor sap that I say that have
some good news and some bad news. “The good news is you do not have scope
creep; the bad news is you are over budget.” What I mean is that since they
never defined scope to begin with they are not outside of scope.

(In a future post, I will visit each of the elements of a
great scope document.)

Even when they do a decent job of developing scope, some
professionals get caught in true scope creep. This happens when after having defined
a good scope, the project manager (professional)
allows more scope to be added to the project without rebalancing the triangle.
In other words, they take on more “What” and they squeeze the “How’s”. This is
what a change request is for, but that will have to be another post.

quod erat


  1. Ed,

    This is a fantastic post on project managment. I’ve always loved your triangle metaphor since you first shared it with me, it’s extremely powerful.

    No doubt one of the “Seven Deadly Sins” of the billable hour is how it lets PKFs off the hook when it comes to project management.

    Your work in this area is inspiring and I look forward to your future posts as a follow-up to this one.

  2. I couldn’t agree more! That’s phenomenal. I adopt this philosophy 100% since learning about it earlier this year. My question is: how do you move current “needy” clients away from the hourly into a value billing mechanism? Any hope for current engagements at an hourly rate? Your insights would be appreciated, Ed.

  3. Ed Kless, Senior Fellow, Verasage Institute says:

    Thanks, Kent for the comment.

    The short answer is to offer on-going support agreement based on a fixed price. Two key elements of the plan will be a certain number of diagnoses and a guranteed response time.

    I would suggest three levels – Gold, Silver, Bronze – with ever increasing numbers of diagnoses and shorter response times as you move up the levels.

    Hope that helps.

  4. Great post! So what is the purpose of the line in the diagram? Thanks.

  5. Mike, the line delineates the “How” vs “What matters” questions.

  6. You have done really nice work by creating such a great post, keep up the good work.

  7. Zaeem Ahmad Siddiqui says:

    I was searching for Triple Constraint and came up to this blog, It’s a great blog to define core constraints in a brief way. But you didn’t include the uncertainties/risk in this article which is I believe one of the basic constraint in relation to this triangle theory. As I read and strongly believe that Project Management key purpose is to handle the uncertainties.

  8. I’m struggling to understand how this diagram actually relates to the concept presented. You wrote, “if you make a change to the value of one of the angles, one of the other two or both must also change to compensate or else the figure is broken”.

    If scope is Angle A, then as the angle gets larger, then the bottom line of the triangle (between B and C, or cost and time) would need to get longer in order that the triangle remains a triangle. This would cause the angles of cost and time to get smaller. In other words, the natural behaviour of the triangle is that as scope increases, cost and time both decrease.

    But of course that is the opposite of what actually happens. As scope increases, cost and time both naturally increase.

    The same mismatch between the geometric nature of the angles in the triangle and what happens in projects exists for the other variables, cost and time. For example, if the angle of cost (i.e. the amount of cost) increases, then the time and the scope angles would both decrease.

    • Thanks for your comment. You are correct, the analogy is a bit of a problem from that standpoint. Alas, that is the trouble with all analogies in that they only represent part of the story.

      In teaching this concept I have learned that the your specific objection can be handled by changing the three variables from representing the angles to representing the lines of the triangle. This way as the line representing scope gets larger, the other lines will need to grow to adjust. Of course, that creates some other problems.

      I hope that helps.

      • Hey Ed, I really appreciate the prompt reply. Thanks for this. I agree that focusing too heavily on the geometric nature of the analogy is probably counter-productive. I think what I’m really struggling with here is just the relationship between these variables as it relates to scope and in particular, value pricing. I came across this concept in Ron’s book, and funnily enough I think the chapter in his book is just this blog post – I hope he covered copyright with you on that first. 😉

        Anyway, is it fair to simply say that the idea here is that as scope increases, both cost/resourcing and time also must increase? That makes sense to me. I think what is tricky for me is the idea that this relationship would bear on other variables – for example, if cost increases, should scope increase? According to the basics of value pricing, it seems the answer is, not necessarily.

        Maybe I’m just rambling a bit at this point. I’m currently implementing value pricing at our company and I want to make sure that when I teach certain concepts, I’ve got a really good grasp on them. I certainly understand the core concepts here around defining scope, ensuring we accommodate changes to cost and time when scope changes, and so on. In any case, thanks for the post and thanks for your reply.

        • Adrian, I think you have thought about this almost as much as me. It is good to know I am not alone in the world. 🙂

          Part of the trouble is the definition of terms. When talking to a customer, “cost” becomes “price.” In addition, Time is always duration, not effort. Therefore, if the Scope increases it is possible that only one of the other two needs to be adjusted. Yes, I could increase price, but I could also extend duration and leave Price (aka Cost) alone. This is why I like the angles better than the lines.

          If you think about the geometry, if one angle “grows” from 60 to 90, I could just change ONE of the other angles to readjust back to an equal angular triangle.

          Again, the trouble is the analogous nature of the concept.


  1. […] scope document which keeps the Triangle of Truth (resources, scope & time) in balance and then maintaining that balance is the art of project […]

  2. […] can you have the difficult conversation when the Triangle of Truth is out of […]

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