Story points vs t-shirt sizing: which scale should you use?
2 min read · Updated on November 3, 2026
Two scales dominate team estimation: story points, usually on the Fibonacci sequence, and t-shirt sizes. Both rest on the same principle, relative estimation, but they serve different needs.
What they share: relative estimation
In both cases, you don’t estimate a duration but the size of a task compared with others. People are much better at comparing (“this is bigger than that”) than at predicting an absolute duration. That is what makes both methods more reliable than estimating in hours.
Story points
Story points are numbers, usually taken from the Fibonacci sequence: 1, 2, 3, 5, 8, 13, 21. They measure the overall effort of a story, combining complexity, amount of work and uncertainty.
- Pro: they add up. You can compute the team’s velocity (points completed per sprint) and use it to plan the next ones.
- Pro: they are precise where it matters, on small stories, and deliberately coarse on big ones.
- Con: numbers invite people to convert them into days or to compare teams, two bad practices.
- Con: they are more abstract for non-technical people.
T-shirt sizes
T-shirt sizes sort work into categories: XS, S, M, L, XL, XXL. Everyone instantly understands that an L is bigger than an S, no explanation needed.
- Pro: very intuitive, they make conversations with business stakeholders and management easier.
- Pro: fast, they let you size dozens of items in one session.
- Pro: with no numbers, there is no temptation to convert them into days.
- Con: they don’t add up. You can’t compute velocity directly unless you assign them values.
Which one should you choose?
It mostly depends on what you will do with the estimate:
- Planning a Scrum sprint: story points, to track velocity and know how many stories to take on.
- Prioritizing a backlog or roadmap: t-shirt sizes, to quickly rough out epics or features.
- A team new to agile: t-shirt sizes, easier to adopt, before moving to points.
- Talking with non-technical stakeholders: t-shirt sizes, which speak for themselves.
Many teams combine both: t-shirt sizes for epics early on, then story points for stories when it is time to plan them.
Going from one to the other
If you need to add up t-shirt sizes, give them a fixed value once and for all, for example XS = 1, S = 2, M = 3, L = 5, XL = 8 and XXL = 13. Keep this mapping stable, or comparisons over time lose their meaning.
In The Planning Poker, you can pick the Fibonacci or the t-shirt sizes deck when creating the room, and switch during the session.