Large / Uncertain / Small
Large / Uncertain / Small (also known as LUS estimation, from Large, Uncertain, Small) is a quick estimation technique that sorts user stories or other work items into just three categories: large, uncertain, and small. It is one of the simplest estimation techniques and can be applied in minutes, even with large backlogs.
When to use it
- At the start of a project, when the team does not yet have a velocity baseline or enough shared experience to use the Fibonacci sequence.
- As a quick first pass over a large backlog, before a more precise estimation with planning poker or Affinity Estimating.
- When non-technical stakeholders who are not familiar with story points take part.
The three categories
- Small: the story is clear, and the team can comfortably complete it within the sprint. Its size is manageable, and it has no significant dependencies.
- Large: the story is too big to be completed in one sprint or needs to be broken down before the team can commit to it. It may be an epic that has not yet been split.
- Uncertain: the team does not have enough information to decide whether it is small or large. The uncertainty may be technical (it is not known how to build it) or business-related (the requirements are not clear enough). Uncertain stories usually need a refinement process before they can be estimated more precisely.
How to apply it
- The stories are presented one at a time.
- The team, by quick consensus or a simple vote, places each one in one of the three categories.
- Small stories can go straight into Sprint Planning.
- Large stories are flagged to be split before the next sprint.
- Uncertain stories are flagged for investigation or refinement: a spike or an additional conversation with the Product Owner may be needed.
Common mistake
Not acting on uncertain stories. The "uncertain" category is the most valuable part of the technique because it makes explicit what the team does not know. If, after the estimation session, the uncertain stories are left pending with no action plan—who is going to investigate? when?—the technique will have produced information but no improvement. Every uncertain story should leave the session with an owner and a date for resolving the uncertainty.
See also
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