In 30 seconds
- Sizes like XS, S, M, L, XL keep estimates deliberately rough.
- Great for roadmaps and early backlog triage.
- Convert to points or time only with care.
How it works
The team sorts items into sizes such as XS, S, M, L and XL by comparing them with each other and a few reference items. Because the sizes are obviously approximate, nobody mistakes them for commitments.
When to use it
- Early roadmap planning
- Triaging a large new backlog, often via affinity estimation
- Talking with stakeholders who find points abstract
For sprint planning, finer story points usually work better.
Converting sizes
For forecasting, teams sometimes map sizes to point ranges, such as S as 1 to 3 and M as 5 to 8. Keep ranges, not single numbers, so the roughness isn't lost.
Myth vs reality
Myth · T-shirt sizes are too vague to be useful.
Reality · Their vagueness is honest for early estimates.
Myth · Every team uses the same mapping.
Reality · Each team defines its own.
Myth · XL items can go into a sprint.
Reality · XL is a signal to split first.
FAQ
How many sizes should we use?
Five (XS to XL) is common; more invites false precision.
Can we compute velocity from T-shirt sizes?
Only after mapping to numbers, and roughly.
Who should size?
The team doing the work.