When to use
Use this playbook once an idea has an approved high-level design. A T-shirt size is a rough range, not a commitment. It gives portfolio prioritization something to weigh value against, and gives Planning a starting point for capacity.
Roles
- Program Manager: leads. You facilitate the session and keep sizes consistent across the portfolio.
- Product Manager: explains the outcome and answers scope questions.
- Product Owners and senior engineers from the affected Home Teams: do the estimating.
The size scale
We count sizes in team-sprints: one team for one two-week sprint.
| Size | Team-sprints | What it usually looks like |
|---|---|---|
| XS | 1 or fewer | A change one team can finish in a sprint |
| S | 2 to 3 | One team, a few sprints, no other teams involved |
| M | 4 to 6 | One team for about a quarter |
| L | 7 to 18 | Two or three teams for about a quarter |
| XL | More than 18 | Several teams or more than a quarter. Split it before Gate 2 |
Work of size S or smaller that stays within one Home Team is usually Discretionary, not a strategic project.
Before you start
- Send the high-level design to the estimators two working days ahead.
- Bring two or three past projects with known actual sizes to use as reference points.
Steps
- Walk through the design. The Product Manager spends 10 minutes on the outcome and the recommended option.
- Estimate silently. Each estimator picks a size on their own and writes it down.
- Reveal together. If everyone agrees, record the size and skip to step 5.
- Discuss the spread. Ask the highest and lowest estimators to explain their thinking. Re-estimate once. If the group still disagrees, record the larger size and note the disagreement as a risk.
- Write down the assumptions. List what the size depends on, such as "reuses the existing claims API" or "no data migration".
- Split XL work. If the size is XL, propose how to split it into projects of L or smaller, each with its own outcome. Each part goes through prioritization separately.
- Record the result in the idea log: the size, its team-sprint range, the assumptions and the date.
Outputs
- A T-shirt size and its team-sprint range.
- A list of assumptions behind the size.
- For XL ideas, a proposed split into L or smaller projects.
Pitfalls
- Treating a size as a deadline. Dates come from Planning, after capacity is known.
- Anchoring. If someone says a number before the silent estimate, the group tends to follow it.
- Forgetting Run work. Team-sprints are for Change work only. Planning sets aside the Run allowance separately.