Agile Estimating using

T-Shirt Size

Agile estimating activity that brings people closer to an agreement when estimating tends to reveal or widen the gap in perception


This technique helps participants learn how to estimate the effort required by a certain task without complicated formulas and without wasting any time. By switching from numerical estimation to estimating based on the t-shirt sizes S-XL, people reach more easily a common ground because unlike numbers, relative estimating allows team members to think in more dimensions—numbers are often associated with time, but t-shirt sizes can represent more complex ideas, including work hours, effort, and complexity.



  • Introduce the activity to the participants and split into teams.
  • Encourage the teams to nominate an observer that will provide the team with feedback regarding the way this techniques was put into practice.
  • Agree upon the sizes’ representation, by giving a few examples, like M stands for things similar to…
  • Join each team and provide the activity link.


  • Participants discuss and decide which t-shirt size is appropriate for each of the 20 activities – daily tasks – written on the cards in the set. The match is done upon how much time and effort the tasks require to be performed.

Debrief (suggested)

  • The observers will present their findings regarding this process.
  • The facilitator may ask the following questions:
    • How helpful do you find this technique?
    • What challenges did you face during this activity? What or who helped you overcome them?
    • What resources do need to implement this approach in your professional activity?



Additional info

This activity follows activity type guide from CARTA

Play in Colltrain

Agile Estimating using T-Shirt Size - Colltrain Library - Activity Description

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