XS, S, M, L, XL, XXL… Not for your wardrobe, but for your backlog. T-shirt sizing is the quickest way to put a rough size on dozens of items.
It is one of the methods compared in our guide to agile estimation techniques for sprint planning. Here is a size chart to reuse as a template, and how to convert sizes into story points or days.
What is T-shirt sizing?
T-shirt sizing is a relative estimation technique in which a team sorts work items into clothing sizes, usually XS, S, M, L, XL and XXL, instead of giving them numbers or hours. Each size stands for a band of effort that combines the amount of work, its complexity and its uncertainty: an XS is a small, well-understood change, while an XXL is too big and too vague to plan and must be split. In agile teams as in project management, T-shirt sizing serves early, coarse estimates: sizing a new backlog, comparing epics on a roadmap or ranking projects in a portfolio, often with non-technical stakeholders in the room. Its strength is speed, since a team can size dozens of items in one meeting. Its limit is that sizes cannot be added up, so on their own they produce neither a velocity nor a date. To plan sprints or budgets, teams map each size to story points, then refine the estimate as the work gets closer.
What does each T-shirt size mean?
Sizes only work if the team agrees on what they mean. Here is a starting chart you can copy:
| Size | Typical meaning | When to use it |
|---|---|---|
| XS | Tiny change, fully understood, no unknowns | Wording or configuration changes, often grouped together |
| S | Small item, clear approach, few unknowns | Fits easily in a sprint next to many others |
| M | Standard item: real work, some uncertainty | Your reference size: most refined stories land here |
| L | Large item with several parts or a known risk | Check the risks and consider splitting before a sprint |
| XL | Feature or small epic, many unknowns | Roadmap level only: split it before it enters a sprint |
| XXL | Epic or project too vague to size | Do not plan it as is: break it down or explore it first |
To turn this chart into your team's estimation template, add a column with one reference item per size, taken from finished work, and compare new items to those references. Without them, sizes drift into personal opinions: as Mike Cohn puts it, "Your view of an XL may not match mine" (source).
When should you use T-shirt sizing?
T-shirt sizing fits whenever speed matters more than precision:
- A new backlog, during discovery or a project kickoff.
- A roadmap: comparing epics and features over a quarter or a year.
- Project and portfolio management: ranking whole projects by size before funding them.
- Workshops with stakeholders: everyone understands S, M and L.
- Teams new to relative estimation: Cohn sees "the ease of getting started" as the primary advantage of T-shirt sizes.
For sprint commitments, which need values that add up, Fibonacci story points take over; our Fibonacci vs T-shirt sizing comparison details the trade-offs.
How do you run a T-shirt sizing session?
- Agree on the references. One known item for at least S, M and L.
- Invite the right people. In the words of the Scrum Guide, "The Developers who will be doing the work are responsible for the sizing." Stakeholders explain, they do not vote.
- Vote privately, reveal together. After a short presentation of the item, everyone picks a size at the same moment, so the first opinion spoken does not anchor the others. This is the core rule of Planning Poker, and it works with sizes too.
- Discuss the extremes. An S next to an XL means people picture different work: let both explain, then vote again.
- Record and flag. Note the size and mark every XL and XXL for splitting.
Planning Poker Online offers a T-shirt scale (XS to XXL) besides the Fibonacci and powers-of-2 scales; the Scrum Master picks it in the vote settings. Other free tools have a T-shirt deck too: our comparison of free Planning Poker tools shows which ones.
How do T-shirt sizes convert to story points?
Cohn's advice is to "put some underlying numbers on them (e.g., Medium=5)", then gradually shift to the numbers themselves. A common mapping on the Fibonacci scale:
| T-shirt size | Story points (common mapping) |
|---|---|
| XS | 1 |
| S | 2 or 3 |
| M | 5 |
| L | 8 |
| XL | 13 |
| XXL | 21 or more, split it first |
Three caveats before you use it:
- The mapping is a convention. Cohn's own example sets a medium at 5 and a large at 10. Write yours down and keep it.
- Converting adds no precision. A converted L is still rough: re-estimate it in points once refined.
- Each team has its own mapping, so points never compare across teams; see what a story point is.
Can you estimate T-shirt sizes in days?
Yes, but only at team level and only as a range. A size measures relative effort, not duration: the same M can take two days for the developer who knows the code and a week for a newcomer. Cohn makes the same point about story points, which correspond to a spread of hours rather than a fixed rate (source).
Two sound ways to get to days:
- Through velocity. Map sizes to points, add them up, and divide by the team's velocity range. With fictitious figures, four M and three L make 4 × 5 + 3 × 8 = 44 points. At 22 to 30 points per two-week sprint, that is 1.5 to 2 sprints, so 3 to 4 weeks. Our guide to sprint velocity explains how to build that range.
- From your own history. For each size, note how long finished items actually took, and use the observed range, never a single figure.
Avoid a fixed table such as "M = 3 days": it ties estimates back to whoever does the work. Our comparison of story points vs person-days covers quotes and budgets.
What are the limits of T-shirt sizing?
- Sizes do not add up. In Cohn's words: "You cannot tell a boss you'll be done in 3 mediums, 4 larges, and 2 petites."
- The scale is coarse. Six sizes cannot separate a light L from a heavy one: fine for a roadmap, too rough for a sprint.
- Sizes drift. The team's M slowly grows unless the reference items are reviewed every few months.
Frequently asked questions
What does T-shirt sizing mean in agile? In agile, T-shirt sizing means estimating work items with clothing sizes, from XS to XXL, instead of numbers or hours. Each size stands for a band of relative effort combining amount of work, complexity and uncertainty. Teams use it for quick, rough estimates of backlogs, epics and roadmaps, then switch to story points for sprint planning.
How do you convert T-shirt sizes to story points? To convert T-shirt sizes to story points, map each size to a value on your point scale and write the mapping down. A common mapping is XS = 1, S = 2 or 3, M = 5, L = 8, XL = 13 and XXL = 21 or more. Apply it consistently, and re-estimate items in points once they are refined.
How many days is a T-shirt size? A T-shirt size has no fixed number of days, because it measures relative effort, not time. To get a duration, convert the sizes to story points and divide the total by the team's velocity range, or use the time the team actually spent on past items of each size. Always give the result as a range.
Can you play Planning Poker with T-shirt sizes? Yes. Planning Poker works with any scale: each voter picks a size privately, everyone reveals at once, and the team discusses the gaps. Planning Poker Online offers a T-shirt scale from XS to XXL alongside the Fibonacci and powers-of-2 scales, chosen by the Scrum Master in the vote settings.
Sources
- Mike Cohn, Estimating with Tee Shirt Sizes, Mountain Goat Software
- Mike Cohn, Don't Equate Story Points to Hours, Mountain Goat Software
- Ken Schwaber and Jeff Sutherland, The Scrum Guide, 2020
Size your backlog in minutes
Want to size your backlog as a team? Create a free Planning Poker session, pick the T-shirt scale and let everyone vote at the same time. No sign-up required. See all the features.
