Fibonacci vs T-Shirt Sizing Agile: Best Estimation Scale
Fibonacci (1, 2, 3, 5, 8, 13) vs T-shirt sizes (XS, S, M, L, XL)—which estimation scale should your team use? The answer depends on your team's comfort with numbers, need for precision, and how you integrate with project management tools.
Fibonacci Sequence Benefits
- Built-in uncertainty: Gaps widen (5 vs 8 vs 13) as complexity increases, reflecting natural uncertainty
- Prevents false precision: No option for "6 points"—forces acceptance that estimation is approximate
- Jira/tooling integration: Most tools default to Fibonacci
- Velocity math is easier: Summing numbers vs. converting shirts to numbers
T-Shirt Sizing Benefits
- Less intimidating: Non-technical stakeholders understand "this is a Large"
- Faster initial adoption: Teams grasp concept immediately
- Better for high-level roadmapping: Sizing epics before breaking into stories
Most teams start with T-shirts for simplicity, then graduate to Fibonacci for precision. Alignlee supports both scales—switch anytime.