Colorful illustration of various sized T-shirts labeled small, medium, and large, representing T-shirt sizing in Agile and Waterfall project management against an abstract wave background

T-shirt sizing in Agile and Waterfall Projects

By: Hajime Estanislao, PMP, CSM

Embarking on project estimations can often feel complex, with an unclear path forward and a high potential for missteps. This is where the concept of t-shirt sizing shines as a simple estimation technique. 

Imagine estimating the scope and effort of your project tasks with the ease of choosing a T-shirt size—XS, S, M, L, XL. This method strips away the complexity of traditional estimation techniques, fostering swift, accessible discussions among team members and paving the way for consensus. It is especially crucial in the early stages of project planning, where precise details might be scarce, yet a general direction is essential. Whether you are maneuvering through the dynamic sprints of Agile or the structured phases of Waterfall, T-shirt sizing adapts seamlessly, offering a versatile tool across industry landscapes.

  • Simplify Complex Estimations – Break down project tasks into manageable, relatable sizes.
  • Facilitate Team Consensus – Encourage collaborative discussion, leveraging the collective wisdom of your team for better accuracy.
  • Adapt Across Methodologies – Whether you are an Agile aficionado or a Waterfall warrior, T-shirt sizing fits snugly into your project management toolkit.

Let us now check the world of T-shirt sizing – one of the project management tools that promises to streamline your planning process and transform it into an engaging, team-building exercise.

By embracing this method, you are setting your projects on a path of clarity, more effective planning, and project success. Let us explore how to integrate T-shirt sizing into your project management methodology and practices, ensuring every task, no matter its size, is tailored to your team’s capabilities and project goals.

"Elegant meeting room with T-shirts neatly displayed on shelves, embodying the concept of T-shirt sizing in project management under soft sunlight."

What is T-shirt Sizing?

T-shirt sizing is a straightforward, informal technique used in project management to estimate the size of tasks or features. Instead of dealing with detailed, often complex numerical values, this method uses the familiar sizes of T-shirts—XS, S, M, L, XL, and so on—to represent the relative effort, complexity, or time requirements of various project components.

By abstracting away from precise measurements, this technique facilitates quicker, more accessible discussions among team members, making it easier to reach a consensus on project estimations. This approach is valuable in the early stages of project planning when detailed information is scarce, but a general understanding of project scope and complexity is essential. T-shirt sizing applies to any project management methodology adapting to many industry contexts.

How It Works

In t-shirt sizing, each story or task is assigned a size based on a comparative analysis of its complexity or effort required compared to other items in the backlog. For instance, a task estimated as a Small (S) would require less effort than one estimated as a Large (L). The specific meaning of each size is subjective and should be agreed upon by the team before the estimation session.


  • Simplicity and Speed – T-shirt sizing is easy to understand and can be conducted quickly, making it ideal for high-level planning sessions.
  • Fosters Collaboration – It encourages team discussion and consensus, as team members must agree on the relative sizing of tasks.
  • Reduces Analysis Paralysis – Focus on relative size rather than exact time estimates; it helps avoid getting bogged down in details early in the planning process.
  • Adaptable – As more information becomes available, Sizes can later be translated into more precise estimates (such as story points or hours).

Reasons You Need to Know T-Shirt Sizing

Understanding T-shirt sizing is an indispensable skill for project managers. It provides a simple way to estimate the size and scope of tasks or features. This method transcends the complexity of traditional estimation techniques, offering a more approachable and universally understandable format. It bridges communication gaps between technical and non-technical stakeholders, ensuring everyone is on the same page regarding project expectations and deliverables.

  • Facilitates Clear Communication – T-shirt sizing helps simplify complex estimations, making it easier for all stakeholders to understand and discuss project requirements and progress.
  • Promotes Quick Consensus – The method allows teams to quickly align on the effort and resources required for tasks, streamlining the planning and prioritization process.
  • Increases Flexibility in Planning – Provides a high-level view of task sizes; T-shirt sizing enables more adaptable and responsive project planning for agile environments.

Whether managing a software development project in an Agile framework or overseeing a service delivery project in a Waterfall context, T-shirt sizing offers a versatile and efficient approach to estimating work, setting the stage for successful project execution and delivery.

"Elegant meeting room with T-shirts neatly displayed on shelves, embodying the concept of T-shirt sizing in project management under soft sunlight."

Step-by-Step to Do T-Shirt Sizing

Implementation Steps for Project Managers

  • Define Size Categories – Establish what each t-shirt size represents based on complexity or effort. All team members must have a shared understanding of this scale. Categories may be XS, S, M, L, and XL.
  • Prepare the Backlog – Ensure the user stories and sizes in the backlog are understood. This may involve a brief discussion of each item before sizing. As part of the development process, refining the backlog and assigning sizes to the tasks and features promotes efficiency in team decision-making.
  • Conduct the Sizing Session – Team members assign a t-shirt size to each backlog item through discussion and consensus or by individual voting (similar to planning poker).
  • Review and Adjust – Once all items are sized, review the assignments to ensure consistency across the backlog. Based on team feedback, adjust any sizes as needed.

Converting to More Precise Estimates

While t-shirt sizes are for initial planning, teams often need to convert these into numerical estimates (like story points) for sprint planning and tracking progress. One approach is to agree on a conversion scale (e.g., XS = 1 point, S = 2 points, M = 3 points, etc.), although the scale can vary based on the team’s velocity and experience.

This process fosters collaboration among team members, facilitates faster decision-making, and streamlines the planning phase. 

Step 1: Define T-shirt Size Categories

Start by establishing what each T-shirt size represents in the context of your project’s success. Generally, sizes range from XS to XL, with each size corresponding to a range of effort, complexity, or duration.

For instance, an XS might indicate a task that takes a few hours, while an XL might represent work that takes several weeks or involves significant complexity. Ensure all team members agree on these definitions to maintain consistency in estimation.

Step 2: List Out Tasks or Features

Compile a comprehensive list of all tasks, user stories, or features that need estimation through a brainstorming session with the project team or by gathering inputs from current project backlogs and stakeholder requirements.

The goal is a clear overview of the work ahead, which will be categorized using the T-shirt sizing method. Tasks and features sizing is an activity for any agile software development project.

Step 3: Conduct the Sizing Session

Meet with the project team, including developers, project managers, and other relevant stakeholders. Present each task or feature to the team and facilitate a discussion about assigning a T-shirt size. Techniques such as silent voting or consensus discussion are used to decide the sizes.

Open discussion is important as different perspectives can help clarify the effort and complexity involved.

Step 4: Review and Adjust Sizes

Once all items are sized, review the assignments as a team to ensure they make sense and adjust any sizes as necessary. This step might reveal some items as too large and thus needing to be broken down into smaller tasks (e.g., splitting an XL task into two L tasks).

This iterative review helps refine the estimations and ensures they are as accurate and realistic as possible.

Step 5: Plan Based on Sizes

Use the T-shirt sizes to inform your project planning and prioritization. Tasks are grouped by size to help determine sprint planning in Agile methodologies or the project lifecycle phases in Waterfall.

This overview allows project managers to allocate resources more effectively, schedule work, and communicate expected timelines to stakeholders.

"Futuristic boardroom meeting with holographic T-shirts floating above a conference table, indicating different sizes as examples of T-shirt sizing in project management."

Further Examples

Team Consensus Method

  • Agile Application – In Agile frameworks, like Scrum, the team consensus method involves all team members in the estimation process. The product owner or project manager presents each feature or task to the team, and members discuss and collectively decide on a t-shirt size. This method leverages team knowledge and fosters collaboration.
  • How to Conduct – Use a roundtable discussion format where each team member shares their perspective on the size of a task based on their experience and understanding. The team then negotiates to reach a consensus on the appropriate t-shirt size.
  • Waterfall Application – While Agile encourages team consensus, this method can also be applied to waterfall projects during the planning phase. Project managers can gather key team members or stakeholders to assess and size project components, helping define the project scope and required resources early on.

Planning Poker

  • Agile Application – Planning Poker combines consensus with gamification to make the estimation process engaging and thorough. Each team member uses a deck of cards with t-shirt sizes (and sometimes numbers) to privately select their estimate for a task. Votes are simultaneously revealed to promote unbiased estimates.
  • How to Conduct – After a task is discussed and sized, each member selects a card representing their estimate. If estimates vary widely, the outliers explain their reasoning, and the process repeats until the team reaches a closer agreement. This iterative approach ensures that all viewpoints are taken into consideration.
  • Waterfall Application – In Waterfall projects, where tasks are more linear and defined upfront, Planning Poker is used during the initial project planning phase. It can help assess the complexity of various project components, contributing to more accurate scheduling and resource allocation.

Dot Voting

  • Agile Application – Dot voting is a quick, democratic way to reach consensus on task sizes. It is useful in larger Agile teams where a consensus through discussion could be time-consuming.
  • How to Conduct – Each team member is given a set of dots (stickers or digital equivalents) and allocates to tasks displayed on a board; each task will have different t-shirt sizes. The size with the most dots at the end of voting is selected. This method highlights the collective intuition on task complexity.
  • Waterfall Application – Although Waterfall methodology is more structured, dot voting can be used in the early stages of project planning. It can expedite the estimation process when a broad overview of project components and their potential complexities is needed, aiding the high-level project timeline.

"Spacious boardroom with multiple screens showing T-shirt sizing charts and data, conceptualizing the implementation in traditional and Agile project management settings."

Implementing T-shirt sizing in Traditional and Agile Project Management

Regardless of the methodology used, t-shirt sizing is an excellent tool for simplifying the estimation process, making it accessible and engaging for all team members. By abstracting the complexity of tasks into more manageable categories, teams can foster better understanding and communication around project scope and requirements. 

When implementing t-shirt sizing, consider the following tips to enhance its effectiveness:

  • Clarify Size Definitions – Ensure all team members understand what each t-shirt size represents in terms of effort, complexity, or duration.
  • Review and Adjust – Regularly review the accuracy of previous estimates and adjust your sizing definitions as needed. This iterative refinement helps improve the reliability over time.
  • Combine it with Other Methods – T-shirt sizing can be used as a preliminary estimation tool, followed by more detailed methods (e.g., story points in Agile or work breakdown structures in Waterfall) for finer planning and scheduling.

T-shirt sizing bridges the gap between different project management approaches by offering a flexible, intuitive method for task estimation. Whether you are managing an Agile sprint or planning a Waterfall project, integrating t-shirt sizing can facilitate smoother project initiation and planning phases.

T-Shirt Sizing Activity Example in Scrum

A software development team is planning its next sprint in a Scrum framework and needs to estimate the effort required for a list of new features and bug fixes. The Product Owner has outlined the requirements, and the team gathers for a t-shirt sizing session.

  • Define Size Categories – The team agrees on what each t-shirt size means, e.g., XS for very small tasks that require minimal effort, up to XXL for massive items that might need to be broken down further.
  • Round of Estimation – The Product Owner presents the first user story: Implement a new login feature with two-factor authentication. After a brief discussion, the team agrees it is a Large (L) effort due to the security implications and testing required.
  • Comparison and Consensus – As more items are discussed, such as bug fixes sized Small and adding a new search functionality Medium, the team references the effort agreed on in the first user story to maintain consistency in sizing.
  • Outcome – At the end of the session, the backlog items are roughly prioritized based on their size. The Scrum Master facilitates a discussion to ensure consensus and ensure that the sprint backlog reflects the team’s capacity.

T-Shirt Sizing Activity Example in Services Industry

A digital marketing team is planning a new campaign that includes various tasks like content creation, social media strategy, and paid advertising setup. To estimate the effort required for each component, they decided to use t-shirt sizing.

  • Define Size Categories – The team defines sizes from XS for tasks like updating a social media post to XXL for launching a comprehensive paid advertising campaign across multiple platforms.
  • Estimation Session – For the task “Create a series of blog posts for the new product launch,” the team debates between Medium and Large, finally settling on Large due to the research and coordination with the product team required.
  • Adjustments – As the session progresses, the team adjusts their understanding of what constitutes a Medium vs. a Large task based on discussions, ensuring a uniform scale of effort.
  • Outcome – The t-shirt sizes help the team visualize the campaign’s scope and prioritize tasks. This aids in sprint planning, where tasks are selected based on priority and team capacity for the upcoming sprint.

T-Shirt Sizing Activity Example in Waterfall Projects

An IT department is planning a system upgrade project using the Waterfall methodology. The project is in phases, and the team decided to use t-shirt sizing to estimate the effort required for activities in the initial planning phase.

  • Define Phases and Tasks – The project is divided into phases, such as Requirements, Design, Implementation, etc., with tasks identified for each phase.
  • Initial Estimation – For a project focusing on developing a new database schema in the Design phase, the team estimates a Medium size after considering the complexity and effort required.
  • Sequential Planning – Unlike Agile, the entire project plan is laid out from the beginning. T-shirt sizes help estimate the effort and duration of tasks sequentially, influencing the project timeline and resource allocation.

Outcome – The t-shirt sizes offer a high-level view of the project’s effort distribution, assisting in detailed planning and scheduling of the subsequent phases. Adjustments to sizes and plans are made as the project progresses through its phases, albeit less frequently than in Agile methodologies. "Bright and airy design studio with T-shirts on display and project plans on the table, highlighting key considerations for implementing T-shirt sizing in projects."

Key Considerations for T-Shirt Sizing in Your Projects

Successfully implementing T-shirt sizing in your projects requires more than just following the steps; it is about embracing the mindset that estimations are collaborative and inherently flexible. One insight is the importance of fostering an environment where all team members feel comfortable sharing their opinions. The value of this technique lies in the outcomes and the discussions; it reveals insights into the work that might not surface otherwise. Ensuring that these discussions are inclusive and respectful is crucial.

Additionally, it’s important to remember that T-shirt sizing is one of the numerous project estimation techniques – it’s more about comparing tasks against each other than defining exact durations or efforts. This relativity should be a constant consideration, helping to guide discussions and decisions. Lastly, it is an iterative process. As projects evolve and more information becomes available, revisit your estimations and adjust as needed, maintaining flexibility and responsiveness to change.

How to Improve and Enhance T-shirt Sizing

Integrating T-shirt sizing with other project management and estimation techniques can help you get more out of it. For instance, after completing the technique, teams can translate these relative sizes into more quantifiable metrics, such as time or story points, for detailed planning and tracking.

It can help with project estimates for abstract sizes with actual development and delivery schedules. Another way to take it to the next level is by using historical data. As you complete more projects, collect data on how long items of each size take. This historical perspective can refine future estimations, making them more accurate and reliable.

Continuously engage the team in refining the T-shirt sizing process itself. Solicit feedback on what’s working and what isn’t, and be willing to adjust the process to suit the team’s needs and project demands. Continuous improvement in the process will lead to better outcomes and more engaged team members.

Alternatives to T-shirt Sizing

While T-shirt sizing is a popular and effective estimation technique, several alternatives may suit teams or projects. Story Point Estimation is one alternative, where tasks are estimated based on complexity, effort, and risk, using a numeric scale (often Fibonacci sequence). This method can provide a more granular view of the effort required. Planning Poker is a gamified version of story point estimation that involves team members voting on task sizes using cards, promoting discussion and consensus.

Each of these alternatives has its strengths and can be selected based on the needs of the project and the team, as well as the level of detail required for the estimations.

"Bright and airy design studio with T-shirts on display and project plans on the table, highlighting key considerations for implementing T-shirt sizing in projects."

Final Thoughts and My Experience with T-Shirt Sizing

This estimation technique offers a unique blend of simplicity and effectiveness, making it an invaluable project management tool for both agile and traditional methodologies.

T-shirt sizing acts as a catalyst for dialogue, bringing team members together to discuss, debate, and reach a consensus on the complexities of the tasks at hand. It aids in building a more accurate project roadmap and strengthens team dynamics and alignment.

From IT to services industries, across agile and waterfall methodologies, T-shirt sizing has proven to be a versatile and adaptable technique. It is applicable in various contexts and capable of accommodating the unique needs of each project.

Through these insights and practical steps, this article aims to equip you with the knowledge and confidence to implement T-shirt sizing in your projects. Whether you are navigating the initial stages of a new endeavor or seeking to refine your existing estimation processes, embracing this estimation technique can lead to more engaged teams, clearer project visions, and, ultimately, more successful business outcomes.


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