T-Shirt Sizing In Agile: Everything You Need To Know

T-shirt sizing in agile is one of the simpler project estimation techniques used by software development teams. Compared to bucket systems or affinity mapping, it’s one of the rougher ways to estimate projects, backlog requirements, and timelines.

T-shirt sizes are assigned according to the available information at the time of the estimation. The technique is often used by development teams for roadmap and release planning, helping them get clarity on the project ahead.

But if t-shirt sizing is merely guesswork, does it really matter? After all, it’s only a rough estimate and ballpark figure.

In short, it’s helpful for planning in the long term. Teams can break projects down into smaller parts and have a better overview of product estimation and capacity planning. When done right, T-shirt sizing can be a great way to avoid estimation oversights.

This guide will outline what T-shirt sizing in agile is, how to use this method in your next project, and its pros and cons.

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What Exactly is T-Shirt Sizing in Agile?

T-shirt sizing in agile is a technique to help with capacity planning and product estimation. In this estimation technique, agile teams estimate initiatives based on T-shirt sizes - such as XS, S, M, L, XL, and XXL. This approach is a form of relative estimation that helps teams understand how much time and effort the initiative will take.

Using T-Shirt sizing for your product backlog is an alternative to numeric ratings. This aims to provide teams with a more dynamic evaluation of the required initiatives or stories. Instead of assigning numeric values, T-shirt sizes let agile team members think in more dimensions.

T-shirt sizing in agile is a general estimation, though, and not entirely accurate. Once a T-shirt size has been assigned, the agile team can look deeper into the initiative and set a numeric value.

The T-shirt sizing agile chart and approach you take can depend on various factors. For example, you can assign T-shirt sizes based on factors like time, effort, or complexity.

The technique of T-shirt sizing in agile is a useful way to manage a large backlog of items. It gives teams a general understanding of the total backlog size and the effort required to clear it.

How Does T-Shirt Sizing Work?

T-shirt sizing in agile is not an exact science. Instead, it allows you to make general relative estimations. Here are the steps you need to take when using this approach for your backlog.

1. Establish T-Shirt Sizes

First, understand what T-shirt sizes you want to use. The larger the scope of your project, the more sizes you want to introduce. However, using fewer sizes (S, M, L, and maybe XL) will make this technique easier to manage - especially when defining smaller projects.

2. Understand What the Sizes Represent

T-shirt sizing in agile will only work if everyone understands what each T-shirt size represents. Ensure everyone is clear on what each size means and how they will be assigned. This should be established in a collaborative discussion with the team.

Understanding this will also involve knowing exactly what factors determine which size. Everyone on the team needs to be on the same page regarding this.

Beyond just establishing what factors the sizes will represent, everyone needs to understand how the sizes relate to each other. For example, S could be twice as small as M or six times as small. Whatever relativity scale you use must be consistent for all sizes.

This is why projects with a larger scope do better with more sizing options. The increased options help to establish the scale better.

3. Determine Who Does the Sizing

Will T-shirt sizing be open to the whole team, or will a single person be in charge of this task? This will depend on your agile team structure.

Generally speaking, the person who determines sizes would be:

  • Agile teams running Scrum: The product owner assigns sizes, and the Scrum master reviews them
  • Product backlogs: The product owner assigns sizes
  • General project teams: Individual team members establish sizes based on the team’s sizing definitions

4. Assign the T-Shirt Sizes

The next step is to assign the T-shirt sizes. This can be done based on a T-shirt sizing agile chart, which displays the value that each size represents.

5. Evaluate the Workload

Once all T-shirt sizes have been established, the team can now estimate and evaluate the workload ahead. This will generally depend on how much time or effort the initiatives require.

Of course, if additional tasks or initiatives are added to the project, they can be sized accordingly. In turn, you can adjust the estimated project scope.

Pros and Cons of T-Shirt Sizing in Agile

Here are some advantages and disadvantages of using T-shirt sizing in Agile.


  • It’s a simple approach that lets agile teams make fast estimations on projects with large numbers of items.
  • A more fun and creative approach toward estimations (different from a more analytical approach)
  • A straightforward way to help teams understand their tasks, priorities, and efforts without implementing deadlines
  • Does not involve strict deadlines, so priorities can be adjusted and extended.


  • T-shirt sizing in agile is not always completely accurate. Numeric value estimations are more accurate, and T-shirt sizes are often converted to numeric values later on.
  • It can be difficult to accurately compare the different sizes to each other.
  • Relative sizes need to be consistent.
  • T-shirt sizing in agile provides rough estimates, so it is not the best tactic to accurately project projects, set deadlines, and hold teams accountable to

Five Hands backs from five different person over a table

Final Thoughts

While it’s not a perfect system, T-shirt sizing in agile is one of the best estimation techniques for many projects. As long as your agile team properly understands the meaning of T-shirt sizes and their relative values, you can use this technique to gauge project requirements easily.

T-shirt sizing in agile is also a fun approach to breaking down complex projects. Team members can easily understand the concept of sizes, which helps to make evaluating project scopes and sprints a lot more straightforward.

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