Estimation: T-shirt sizing

⏱ 3 min  ·  📅 2026

T-shirt sizing is a relative estimation technique that classifies user stories or other work items into size categories using the metaphor of clothing sizes: XS, S, M, L, XL, XXL. Its main advantage is that it is intuitive for people with no prior experience in agile estimation, including non-technical stakeholders.

The sizes

• XS / S (Small): work that can be done in a few hours or a day.
• M (Medium): work that may take a few days.
• L (Large): work that may take a week or more.
• XL / XXL (Extra Large): work that requires several weeks or more. It often indicates that the story should be split into smaller stories.

These categories are flexible: each team can adjust its scale to the needs of the project.

How to apply it

1. Preparation: hold a meeting with all relevant team members and stakeholder representatives. Make sure everyone understands the technique before starting.
2. List of stories: identify all the stories to be estimated. Present each one with enough context to allow clarifying questions.
3. Individual estimation: each member independently assigns a size to each story.
4. Discussion: share the estimates and discuss any discrepancies. The goal is consensus, not unanimity.
5. Reference story per size: select a representative story for each size to use as a calibrator in future estimations.
6. Documentation: record the agreed estimates.

When to use it

• In the early stages of a project, when the stories still have little detail.
• In conversations with non-technical stakeholders, where talking about "story points" causes confusion.
• Before a more precise planning poker session, to make a quick first pass over a large backlog.

Common mistake

Not calibrating sizes with reference stories. If the team does not explicitly agree on what an "M" or "L" story is, using specific examples, each member applies their own judgement and the estimation loses consistency. The reference story does not have to be perfect. It only has to be a story that everyone has seen completed and whose relative size they all agree on.

Resources

📄 Técnicas de estimación ágil: tres estrategias [Agile estimation techniques: three strategies, in Spanish]Scrum Manager Blog · Jul 2023

See also

Planning poker Affinity Estimating Bucket System Wall estimation NoEstimates Story point Work item

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