T-Shirt Sizing in Agile

T-shirt sizing is an estimation technique that replaces numbers with familiar clothing sizes: XS, S, M, L, XL and XXL. Instead of arguing whether a task is a 5 or an 8, the team simply agrees that it feels like a medium or a large. Because everyone already understands that a large is bigger than a medium, the technique is easy to explain and works well with stakeholders who do not think in story points.

The sizes and what they usually mean

Fun Fox Planning Poker offers six sizes. The exact meaning is up to your team, but a typical interpretation looks like this:

XS: a tiny change, such as a copy fix or a configuration tweak, with almost no risk.
S: a small, well-understood task that one person can finish quickly.
M: a normal story with a few moving parts. This is often the team’s baseline.
L: a larger story touching several areas or with some unknowns.
XL: a big item with real uncertainty that should probably be split.
XXL: too big to plan as it stands. Treat it as an epic and break it down.

When to choose T-shirt sizes

T-shirt sizing shines when precision would be false precision. It is a good fit for roadmap planning, early backlog grooming and discovery work, where items are still vague and the question is simply which ones are cheap and which are expensive. It also suits new teams that have no velocity history yet, and mixed groups where product, design and business people take part in the discussion.

T-shirt sizes versus Fibonacci

Fibonacci story points give you numbers you can add up, which makes sprint capacity and velocity calculations straightforward. T-shirt sizes are looser: you cannot sensibly add two mediums and a large without first deciding what they are worth. That makes sizes better for coarse, early estimates and numbers better for committing to a sprint. Many teams use both: sizes while the backlog is rough, then points once a story is close to being scheduled. Our Fibonacci story points guide covers the numeric approach.

Converting sizes to story points

If you need numbers, agree on a mapping once and write it down. One common mapping uses the Fibonacci sequence:

XS = 1
S = 2
M = 3 or 5
L = 8
XL = 13
XXL = 21, or split the item before estimating it

There is no universal standard, so treat this as a starting point and calibrate against stories your team has already finished. What matters is that the mapping is consistent, not that it matches another team’s table.

Tips for running a T-shirt session

Pick one or two finished stories as reference points for each size before you start.
Vote privately and reveal together, just like in regular planning poker, so nobody anchors on the first size spoken aloud.
Discuss the gap when votes are more than one size apart, for example S against XL. Those conversations expose missing context.
Split anything sized XL or XXL, then re-estimate the smaller pieces.
Do not do arithmetic on sizes until you have converted them to points.

A quick example

Imagine a backlog with three items: changing the label on a button, adding a CSV export to an existing report, and building a new notification system. The team votes and reveals together. The button label is an easy XS. The CSV export draws an M from most people but an L from one developer, who points out that the report query is slow on large accounts. That single comment is worth the whole exercise, because the team can now agree on L and note the performance risk. The notification system lands at XXL, so instead of estimating it further, the team schedules a short session to break it into smaller stories.

Choosing what works for your team

Neither approach is better in every situation. If conversations about exact numbers keep stalling, try sizes. If you need to forecast how much fits into a sprint, move to points. In Fun Fox Planning Poker you can switch the voting system for a room before the first vote is cast, so it is easy to try both with your team.