What are Project Assumptions?

Do you know what the difference between Project Assumptions, Constraints and Dependencies is?

As a young Project Manager I was always confused about 3 Project Management terms.  I was confused about the meaning of Project Assumptions, Project Constraints and Project Dependencies. I could not differentiate one from the other. I used to think that it hardly makes a difference if one term is replaced with another.

I have learned many things in professional life since my early days. However, when I interact with  many other Project Management Practitioners, I can sense that similar kind of confusion confounds them. Let me try to bring some clarity around these simple looking, confusing terms. Believe me, they are simple English words. They have been made difficult by Project Management Experts.

In this post I will talk only about Project Assumptions. I have written other two posts on Project Constraints and Project Dependencies. After reading all three posts, you would be able to understand the finer points about these terms and recognize the difference. These three terms have immense utility in Project Management if they are used appropriately.

What are Project Constraints?

What are Project Dependencies?

What are Project Assumptions?

According to PMBOK® Guide 5th Edition, Project Assumption is “A factor in planning process that is considered to be true, real or certain often without any proof or demonstration”.

Another definition could be “Project Assumptions are events or circumstances that are expected to occur during the project life-cycle”.

You can also look at Max Wideman’s Glossary for the definition of Project Assumptions.

It simply means that some things are supposed to be true. We, as human beings, work on some presumptions and suppositions. Sometimes these Project Assumptions come out to be true while at other time…Alas! they prove to be false.

Let’s understand Project Assumptions through an example.

Situation – PM requires an Approval on Design Artifacts from the Customer during the course of the project. Project cannot move ahead without this Approval.

Project Assumption – “Approval is likely to come within 2 weeks of submitting the Design Artifacts.”

Only time will tell if the above Project Assumption holds true. However, much before that, Project Plan is prepared based on similar Project Assumptions. Project Team must do a complete Analysis before documenting the Project Assumptions and preparing the Project Plan.

Let us talk about few key points which can help in analysis of Project Assumptions.

  • A Project Assumption is believed to be true either through Experience or high-level Historical Data.
  • A Project Assumption is stated without any empirical evidence.
  • All Project Assumptions are potential risks. Assumption Analysis is one of the important techniques for Risk Identification.
  • Project Assumptions should be well Documented and well Communicated. Poor Communication of Project Assumptions can, sometimes, lead to Project Failure.
  • Project Assumptions can be documented in any formal Document but preferably they should be documented in a separate Project Assumptions Log.
  • Bigger Project Assumptions must be Validated with other Stakeholders.

Over To You

But, I still cannot fully understand how Project Assumptions are different from Project Constraints and Project Dependencies?

You will have to read my posts on Project Constraints and Project Dependencies to understand the difference. Do leave a comment, if there is still some confusion.

A question for the readers. Is following statement an Assumption or a Fact?

“There would always be few Assumptions in every Project”

Related Articles

Difference Between Similar Project Management Terms

18 thoughts on “What are Project Assumptions?”

  1. Thanks for clarifying the difference between the three terms with this post. It’s definitely confusing at times, especially using textbook definitions (like lawyer’s legalese!). Simple English words made difficult! And, in practice, they may often be used interchangeably without consequences. But is good to reflect at what the differences really are. I look forward to the next articles on Dependency and Constraint.

    • Thanks Peter. I have posted article on Constraints. Please provide your valuable feedback for that as well. You can look forward to my article on Dependencies in a day or two. I am planning to write a fourth article in series. You can also subscribe to blog posts by entering your email id at top right of this website.

  2. Well its a good feedback on Assumptions. It is true that sometimes even simple terms in project management seems like same & replacable to each other.
    regarding your question, believe answer is “Fact” since in each project there are one pe the other Assumption without which we may not plan & schedule the activities.
    Kindly provide your feedback on this reply. Thanks.

  3. what could be the assumption on the project of growing nuts and vegetable and make peanut butter. I would like to realy understand this term correctly.

    • Assumption 1 – Availability of fertile grounds
      Assumption 2 – Availability of seeds for a reasonable cost
      Assumption 3 – Timely rains (depending on the country where you are growing the nuts and vegetables)
      Assumption 4 – No floods during the period that the crop matures


  4. Hi praveen,

    What could be the assumptions for a project on launching a new payday loan product in the state of Chicago?

    Thanks in advance!

    • Hi Noel,

      I have very little knowledge of loan products and Chicago. Since every project is unique, you would be the best person to determine the assumption for your project. Having said that let me give you few hints for finding the assumptions:
      1. If you do not have the market research data, there will be assumptions related to product success, market penetration, number of potential customers, number of actual customers, demographics etc.
      2. There could be assumptions related to timeframe, cost, marketing strategy etc. for launching your product.
      3. There could be assumption related to customer issues, customer support etc.

      Basically, assumptions will come whenever you do not have hard data (evidence). If you have data (current or historical), then it will not be an assumption.

      Hope it helps.


  5. hello sir,
    i have a scenario ,can you suggest me what might be assumptions here?
    Two small departments, which currently are separate, will be merged into one large department. As a result, it is necessary to combine these two small departments’ information systems.
    Your job is to manage the project to combine two employee databases. The Department of Trade has just under 5,000 employees, while the Department of Business has approximately 8,000 personnel. There are several challenges with this project. Firstly, the two departments use totally different database technologies. Secondly, the employee data in both employee databases are known to be very ‘dirty’: that is, each database contains many inaccuracies and there is much information missing. For example, a survey has found that employee addresses are wrong in about a 25% of the Department of Trade staff records and 40% of Department of Business records. Thirdly, there are weaknesses in relation to the security of both employee databases. Indeed, employee data from the Department of Trade is believed to have been stolen by hackers. Subsequently, the government wants to more effectively protect data within the new combined system.

    Thanks a lot.

  6. Hi Praveen,

    Adding to what you have already mentioned.

    Project Scope Statement, after it gets approved, becomes a part of the scope baseline. So assumptions, constraints and whatever else is in the Project Scope Statement becomes a reference for the project.

    The distinction between charter and scope statement is not only based on high level and low level of detail.

    Best Regards,

    • Hi Almesh,

      Thanks for the comment. Project charter & scope statement are very different documents. There is no comparison. Project charter authorizes the project whereas scope statement provides complete details of the project work at hand.


  7. Hi Praveen,
    An interesting article. I’ve been working as a PMO Manager for a number of years and I always remind my teams that “Assumptions are the mother of all…..” – you may know the rest. Assumptions are fine during the planning stage, but personally, I don’t allow them to be part of my PMS. I always understood the need for them for the deal teams who potentially don’t have access to all the relevant data and they need to make assumptions from a cost perspective, but when delivering against a defined scope, each assumption should all be validated at the outset and translated into the appropriate control component (e.g. risk, issue, change and / or dependency). Personally, I prefer not to have assumptions as a working principle as these will have the real potential to jeopardise the successful delivery of a project if working against a working assumption that is fundamentally wrong. Just my view of the world. Thanks, Jens

    • Jen, I completely agree. Many times, assumptions become excuse for poor project management. Assumptions have a place in PM bu they should be properly validated.

      BR, Praveen.

    • Aiah,

      Assumptions are never developed. They just come because of planning and other factors. You identify and note the assumptions.

      BR, Praveen.


Leave a Comment