Two popular approaches, two different philosophies. Which one fits your team?
At a glance
| Criterion | Fibonacci | T-Shirt Sizing |
|---|---|---|
| Precision | Finer-grained | Deliberately coarse |
| Learning curve | A few sprints | Immediate |
| Best suited for | Sprint planning | Scoping, roadmap |
| Debates generated | Sometimes intense | Usually quick |
| Converts to velocity? | Yes | With difficulty |
Fibonacci: for teams that want relative precision
Fibonacci allows more nuanced distinctions. The gap between a 5 and an 8 is meaningful. That granularity is useful to plan exactly what a team can pull into a two-week sprint.
It is the recommended method for mature Scrum teams that want to track their velocity over time.
T-Shirt Sizing: for speed or for newcomers
T-Shirt Sizing shines in exploratory phases. When you're discovering a new product, building a roadmap, or bringing non-technical stakeholders into the conversation, clothing sizes are more intuitive.
You don't need to explain Fibonacci to a marketing director. Everyone knows what an XL is.
Can you combine the two?
Yes, and it's even a good practice:
- T-Shirt Sizing for the coarse backlog estimation during scoping
- Fibonacci (via Planning Poker) for the fine-grained estimation of tickets pulled into the sprint
Rule of thumb: Pick the method your team understands and actually uses. The best estimation technique is the one that's applied with discipline, not the one that's theoretically perfect.
