How to Get the Best Estimates for Story Size

Estimating story size is a critical part of Agile planning. When done well, it allows teams to plan sprints effectively, align on priorities, and deliver value consistently. However, achieving accurate estimates can be challenging, as it requires a blend of technique, collaboration, and practical judgment.

In this guide, we’ll explore strategies to improve the accuracy and reliability of story size estimates, helping your team set realistic expectations and achieve better outcomes.

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Why Accurate Estimates Matter

Accurate story size estimates:

• Improve Planning: Teams can confidently plan their capacity for upcoming sprints.
• Align Stakeholders: Clear estimates help manage expectations with stakeholders and product owners.
• Mitigate Risks: Identifying overly large or complex stories early reduces the risk of delays.

But estimates are rarely perfect—and that’s okay. The goal is to make them as informed and reliable as possible.

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Tips for Achieving Better Story Size Estimates

1. Focus on Relative Sizing, Not Precision

Rather than trying to estimate in exact hours or days, use relative sizing techniques like Planning Poker. This approach compares tasks to one another, making it easier to identify which are larger or smaller in effort.

For example:

• If Story A is a “3” on the Fibonacci scale and Story B feels twice as large, it might be a “5” or “8.”
• This helps the team focus on comparative complexity instead of absolute time.

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2. Break Down Large Stories

If a story feels too big to estimate confidently, break it down into smaller, manageable pieces. This not only improves estimation accuracy but also:

• Highlights dependencies and risks.
• Makes progress easier to track.
• Ensures work can be completed within a sprint.

For example:

• Original Story: “Build a checkout system.”
• Smaller Stories:
  • Design the checkout page.
  • Integrate payment APIs.
  • Implement order confirmation emails.

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3. Include the Whole Team

Story estimation is a collaborative process. Involve all relevant team members, such as developers, testers, and designers, to:

• Gather diverse perspectives.
• Identify hidden complexities.
• Ensure buy-in and alignment on the final estimate.

This collaborative approach leads to more comprehensive and accurate estimates.

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4. Account for Unknowns

Some stories may have elements of uncertainty or ambiguity. Instead of skipping these stories or assigning arbitrary estimates, try the following:

• Add a Buffer: Include a small additional effort to account for potential surprises.
• Create a Spike: Use a separate research or exploratory task to investigate unknowns before estimating.

For example:

• Spike Task: “Research third-party authentication APIs.”
• Follow-Up Story: “Integrate the selected API.”

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5. Use Historical Data

Review past estimates and compare them to actual outcomes. This historical data can help your team:

• Identify patterns in over- or under-estimation.
• Adjust future estimates based on similar tasks.

For instance:

• If “Design a login page” was estimated as a “3” but required more effort, similar tasks can be estimated higher going forward.

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6. Discuss Assumptions

Clarify and document assumptions behind each estimate. Assumptions might include:

• Availability of resources.
• Tools or technologies involved.
• Scope of the task.

When assumptions are explicitly stated, the team can:

• Revisit them if they change.
• Adjust estimates accordingly.

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7. Avoid Anchoring

Anchoring occurs when one person’s estimate influences others. To avoid this:

• Use silent estimation techniques, such as Planning Poker.
• Reveal all estimates simultaneously to encourage independent thinking.

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8. Refine Estimates During Sprints

Estimates should be revisited during sprint planning or backlog refinement sessions. As more information becomes available, the team can:

• Adjust estimates for greater accuracy.
• Split stories further if necessary.

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Tools and Techniques for Better Estimation

Planning Poker

This popular method helps teams assign story points through collaborative discussion and relative sizing.

T-Shirt Sizing

A simple and intuitive approach using categories like XS, S, M, L, and XL for estimation.

Three-Point Estimation

Incorporates optimistic, pessimistic, and most likely scenarios to create a weighted average estimate.

Historical Velocity

Track the team’s past performance to guide future estimates and sprint capacity.

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Common Challenges and How to Overcome Them

Challenge: Stories Are Too Vague

• Solution: Clarify acceptance criteria and expected outcomes before estimating.

Challenge: Team Members Have Differing Opinions

• Solution: Facilitate open discussions to uncover differing perspectives and reach a consensus.

Challenge: Estimates Are Frequently Off

• Solution: Use retrospectives to analyze estimation gaps and refine the process.

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Final Thoughts

Getting the best estimates for story size requires a mix of structured techniques, team collaboration, and continuous improvement. By focusing on relative sizing, breaking down large tasks, and leveraging historical data, your team can create estimates that guide effective planning and successful delivery.

Remember, the goal of estimation isn’t perfection but consistency and informed decision-making. With these tips and tools, your team can improve their estimation accuracy and build a smoother Agile workflow.