15 September, 2022

What is T-shirt Sizing? | Video

By Mike Clayton


T-shirt sizing has become a popular method for estimating in agile projects. So, In this video, I answer the question, what is T-shirt Sizing?

This video is safe for viewing in the workplace.

This is learning, so, sit back and enjoy

T-shirt Sizing

T-shirt sizing is a simple and popular way to estimate the relative scales of different pieces of work. The method is usually used in agile projects and applied to User Stories.

The estimates are rough and ready, and give a first indication of the scale of work. They are less precise than full estimates or even other agile approaches, like Planning Poker, for example.

Typical T-shirt Sizes

Typically, we assign a T-shirt size to each item of work. Different users have different sizes, but a common approach might use sizes:

  • Extra Small (XS)
  • Small (S)
  • Medium (M)
  • Large (L)
  • Extra Large (XL)
  • Extra Extra Large (XXL)

Good Practice in T-shirt Sizing

In general, the more different sizes you use, the more variation you will get in how people interpret the terms. So, S, M, and L are the core sizes and you would be wise to resist the temptation to add too many more.

It is good practice to work through a few ‘type’ examples first, which you can use to establish a consensus of what, say, S, M, and L look like.

Interpreting T-shirt Sizes

There are different ways that teams can interpret the sizes.

Fibonacci Numbers

But they often use Fibonacci numbers in the same way as Planning Poker, so, perhaps, in units of work:

  • XS – 1
  • S – 2
  • M – 3
  • L – 5
  • XL – 8 
  • XXL – 13

Estimating from Iterations

Maybe the team will relate them to the number of iterations, or sprints, they will need, to develop the functionality:

  • XS < 1
  • S = 1
  • M = 2-4
  • L = 4-8
  • L = 8+

The T-shirt Sizing Process

  1. Agree on your sizes and their definitions, and then make your T-shirt size cards
  2. The Product Owner explains the user story that needs an estimate. The development team asks questions to gain the understanding they need.
  3. Each developer gives the user story a t-shirt size.
  4. All developers raise their cards simultaneously.
  5. The development team discusses the differences and the product owner offers further clarification, if necessary.
  6. The team repeats Steps 3-5 until they agree on the size.

The Benefits of T-shirt Sizing

  • Forcing the estimate into a small, fixed set of sizes means the process is informal and quick.
  • It is very effective for getting an idea of what tasks in your backlog are similar sizes. This is sometimes called ‘affinity mapping’.
  • Popular and fun.

Carefully curated video recommendations for you:

Other videos that answer the question, ‘What is or are…


What Kit does a Project Manager Need?

I asked Project Managers in a couple of forums what material things you need to have, to do your job as a Project Manager. They responded magnificently. I compiled their answers into a Kit list. I added my own. 

Check out the Kit a Project Manager needs

Note that the links are affiliated.

Learn Still More

For more great Project Management videos, please subscribe to the OnlinePMCourses YouTube channel.

If you want basic Management Courses – free training hosted on YouTube, with 2 new management lessons a week, check out our sister channel, Management Courses.

For more of our Project Management videos in themed collections, join our Free Academy of Project Management.

For more of our videos in themed collections, join our Free Academy of Project Management

What is T-shirt Sizing? | Video Click To Tweet

Never miss an article or video!

Get notified of every new article or video we publish, when we publish it.

Mike Clayton

About the Author...

Dr Mike Clayton is one of the most successful and in-demand project management trainers in the UK. He is author of 14 best-selling books, including four about project management. He is also a prolific blogger and contributor to ProjectManager.com and Project, the journal of the Association for Project Management. Between 1990 and 2002, Mike was a successful project manager, leading large project teams and delivering complex projects. In 2016, Mike launched OnlinePMCourses.
{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}

Never miss an article or video!

 Get notified of every new article or video we publish, when we publish it.

>