How Small Should a User Story Be?

“How small a user story should be?” is a question that every agile team faces eventually.

How small is small enough? And when should we break stories down?

The wrong approach can leave teams bogged down in vague, oversized stories—or drowning in detail long before it’s needed. Either way, flow suffers.

This post provides a practical approach to sizing, timing, and collaboration, without overcomplicating the basics.

Stories Often Start Big—and That’s OK

Stories often originate from Product Owners or stakeholders. They might emerge during a story mapping workshop, a customer conversation, or while sketching out a product roadmap. But that doesn’t mean developers should wait passively.

Anyone can—and should—suggest user stories.

Some of the best slices of value come from developers who see a more straightforward path, a better cut, or a new insight.

That said, stories usually start large. We often refer to these as “epics.” There’s no need to slice everything into delivery-ready detail from the start. That’s what refinement is for.

Refine Just in Time

A common trap is trying to refine too much, too early. Agile teams sometimes fall into the habit of treating backlog refinement like a planning factory—breaking down dozens of stories long before they’re needed.

Instead, treat refinement as a just-in-time activity. Break large stories down shortly before they’re likely to be implemented—a sprint or two ahead at most.

This approach has two big advantages:

1. More time for delivery – You spend less time preparing for work that might change or never be done.
2. Better insights – When you get closer to implementation, you’ll usually have a clearer view of what matters—customer needs, system constraints, edge cases.

How Small Is “Small Enough”?

By the time a story is pulled into a sprint, it should:

• Take no more than 1–2 days to complete and demonstrate
• Represent a thin, vertical slice of value
• Include clear, testable acceptance criteria
• Be understood by both the developers and the Product Owner

If a story feels too big or vague during sprint planning, it probably wasn’t ready.

Refinement Is a Team Sport

Refinement isn’t just the Product Owner prepping a backlog. It’s a collaborative exploration between the Product Owner and the developers.

Together, they:

• Break down large stories into smaller ones
• Add detail where needed—without over-specifying
• Clarify acceptance criteria
• Surface questions, risks, and dependencies

Subject matter experts can be brought in as needed—but refinement should be a regular part of the team’s own rhythm.

Short, frequent refinement sessions (e.g. twice a week) work better than infrequent, bloated ones. The goal is clarity, not completion.

Summary: Keep It Lean, Keep It Live

Here’s the core idea:

Start big. Slice when it matters. Refine with the people who’ll actually build it.

A good backlog isn’t a detailed document—it’s a living system that evolves with learning, feedback, and collaboration. Don’t overload it with guesses. Don’t let it atrophy.

Keep it light. Keep it relevant. Keep it just in time.

In our Certified Scrum Product Owner course we go deeper into this topic and learn about patterns for splitting large user stories into smaller ones.