Fibonacci Estimation

Ruth Hadari
Ruth Hadari
Agile Advocate, Engineering Ops Expert
Posted on
Jun 14, 2022
Updated on
Jul 3, 2022
Table of Content

Estimation is important for planning a Sprint or release. In traditional waterfall models, estimates are often made using the bottom-up approach, where developers provide detailed estimates for their tasks. 

However, in Agile, the top-down approach is more common. This means that the Product Owner provides a high-level estimate of the effort required for the entire project, and the team then breaks this down into smaller chunks.

In this article, we will shed some light on the Fibonacci Agile estimation technique. This is a popular way to estimate the effort required for a task in Agile, and it can be used for both small and large projects.

What is Fibonacci Agile Estimation?

Fibonacci estimation is a top-down technique that uses the Fibonacci sequence to estimate the effort required for a task.

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding numbers. This sequence starts with 0, 1, 1, 2, 3, 5, 8, 13, 21… As you can see, each number in the sequence is roughly 1.6 times bigger than the previous number.

In Fibonacci estimation, the numbers in the sequence are used to estimate the size of a task. For example, if a task is estimated as an 8, it means that it will take approximately 8 times as much effort to complete as a task that is estimated to be a 1.

The advantage of this technique is that it forces the estimator to think about the relative sizes of tasks. It also considers that larger tasks are usually more complex and therefore take longer to complete.

When Should Fibonacci Estimation Be Used?

Fibonacci estimation can be used for both small and large projects. However, it is most commonly used for larger projects with greater uncertainty about the required effort.

When an Agile team estimates the effort required for a task, they will often use a planning poker technique: each team member is given a deck of cards with the Fibonacci sequence on them, and they must choose the card that represents their estimate. The advantage of this technique is that it forces team members to discuss their estimates and reach a consensus.

Why Is It Used in Agile Estimation?

There are several reasons why the Fibonacci estimation is popular in Agile:

1. Firstly, Agile is a top-down approach, which means that it starts with a high-level estimate and then breaks it down into smaller pieces. This contrasts with the bottom-up approach used in traditional waterfall models, where developers provide detailed estimates for their tasks.

2. Secondly, it recognizes that larger tasks are usually more complex and therefore take longer to complete. This is important in Agile because teams often have to make trade-offs between different tasks to meet their deadlines.

3. Thirdly, it is easy to use and understand. This is especially important in Agile environments where there is often a lot of uncertainty about the effort required for a task.

4. Finally, it is flexible and can be used for both small and large projects.

Why Is the Modified Fibonacci Sequence Used When Estimating in Safe Agile?

SAFe or Scaled Agile Frameworks is an extension of the Agile framework designed for large enterprises.

The modified Fibonacci sequence used when estimating in SAFe Agile starts with 0, ½, 1, 2, 3, 5, 8, 13, 20, 40, 100… While the first few numbers are similar to the traditional Fibonacci sequence, the larger numbers are rounded up.

The modified Fibonacci sequence is often used when estimating in SAFe Agile because it considers that larger tasks are usually more complex and, therefore, difficult to estimate. This is important in SAFe Agile because large teams often have to make trade-offs between different tasks in order to meet their deadlines.

The advantage of using the modified Fibonacci sequence is that it is easy to use and understand. This is especially important in SAFe Agile environments, where there is often a lot of uncertainty about the effort required for a task.

Other Estimation Methods (Fibonacci Sequence Alternatives)

Several other estimation techniques can be used, such as the T-shirt sizing method, the ideal days method, and the story point estimation technique:

1. The T-shirt sizing method is where each task is assigned a size based on its complexity. For example, a small task might be considered an S, while an enormous task might be considered an XL.

2. The ideal days method is where you estimate the effort required for a task by considering how long it would take to complete if there were no interruptions or distractions.

3. The story point estimation technique is where you estimate the effort required for a task by considering the number of “story points” it would have. Story points are a measure of the complexity of a task and are often used in Agile estimation.

How to Use Fibonacci Estimation in Agile?

Teams can use several methods to estimate using the Fibonacci sequence:

1. The most common method is to use planning poker. Each team member is given a deck of cards bearing the Fibonacci sequence, and they must choose the card representing their estimate. The advantage of this technique is that it forces team members to discuss their estimates and reach a consensus.

2. Another method is a technique called point-wise estimation. This is where each team member assigns a point value to each task based on their estimate of the effort required. The advantage of this technique is that it is quick and easy to do.

3. Finally, you can also use a spreadsheet or any other software tool to help you estimate using the Fibonacci sequence. This is especially helpful if you have a large project with many tasks.

Final Thoughts

No matter which method you choose, it is important to remember that the Fibonacci sequence is only a guide. It is not an exact science, and there will always be some uncertainty when estimating using this technique.

Nevertheless, using the Fibonacci sequence correctly can be an effective way to estimate the effort required for a task.

FAQ:

1. How do you use Fibonacci for story points?

To use Fibonacci for story points, you need first to understand the concept of a story point. A story point is a measure of a task’s complexity. It is often used in Agile estimation because it allows team members to estimate the effort required for a task quickly.

Once you understand story points, you can estimate the effort required for a task using the Fibonacci sequence. The advantage of using this technique is that it is quick and easy to do.

2. Why are Jira story points considered Fibonacci?

Jira is a popular software tool often used in Agile project management and estimation. The Jira story points are considered Fibonacci because the sequence is a quick and easy way to estimate the effort required for a task. This leaves less room for estimation errors, especially for large, complex tasks.

About the author

Ruth Hadari
Agile Advocate, Engineering Ops Expert

Highly experienced in leading multi-organizational teams, groups, in-shore as well as off-shore. The go-to person who is able to simplify the complex. An agile advocate, experienced in all common methodologies. Responsible for the entire software development lifecycle process from development, QA, DevOps, Automation to delivery including overall planning, direction, coordination, execution, implementation, control and completion. Drives execution, and communicates on status, risks, metrics, risk-mitigation and processes across R&D.

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