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May 20, 2022
10 min read

Why Product Backlog & Sprint Backlog Should be Estimated as Two Different Units

Product backlog and sprint backlog are two backlogs with different purposes. Estimating them is vital to have a better team understanding of the lined-up work.
Anton Versal
Anton Versal
Learn how you should estimate Product & Sprint Backlogs

The software industry is in full swing in the present era. Ever-growing customer demands are urging software firms to adopt smart and fast development approaches for fast releases. Owing to that, most software firms are using Agile for fast and responsive work. Agile teams orient themselves around the Scrum framework to ensure iterative-based collaborative development.

Scrum-based development has many unique aspects that helps the team to remain organized. One such aspect is the estimation of both product backlog and sprint backlog. Both these backlogs and their estimations help the team to have a better picture of the efforts and lined-up work. However, there is a misconception about whether product backlog and sprint backlog should be estimated as one unit or two separate units. So, this article will emphasize around this point and help you understand why it is important to estimate product backlog and sprint backlog as two different units.

Product Backlog – A Brief Overview

Before initiating a project, the Product Owner first sets up a list of features that are targeted to be completed in the project. That list is known as product backlog. The product backlog lets the teams understand the whole dimensions of the project. Moreover, it also breaks down all the tasks required for every item on the list. Mostly, a product backlog contains items like bugs, general tasks, and user stories.

Sprint Backlog – A Brief Overview

A sprint backlog is the list of items that the team is targeted to complete in the current sprint. The sprint backlog is mostly created during the sprint planning meeting. During that meeting, the team picks up the items from the long list that they target to complete in the current sprint. An accurate sprint backlog gives teams the right time to complete all the lined-up work.

Product Backlog vs. Sprint Backlog – Key Differences

Although both backlogs enable the team to have a clear glimpse of what they have to work on, still there are plenty of differences between them. A few key differences are listed below:

  1. Product backlog presents the list of all those items that should be completed in the project, while sprint backlog presents the list of all those items that should be completed in the current sprint.
  2. Product backlog is specific to the end goal, while sprint backlog is specific to the sprint.
  3. Product backlog can witness some amendments, but sprint backlog mostly remains as it is. If the team faces any issue during the sprint, that issue is added up in the product backlog in order to address it in the next sprints.
  4. Product backlog is a large list of items and takes time to understand, while sprint backlog is a small list of items and is easy to understand.
  5. Product backlog is created by the product owner, while sprint backlog is created by the Scrum team.
  6. Product backlog is an independent backlog, while sprint backlog is dependent on the product backlog.
  7. Product backlog is maintained by the product owner throughout the project, while a new sprint backlog is created during the start of every new sprint.

To sum up, you can consider product backlog as an album containing multiple songs, while sprint backlog as just one song.

Why It is Essential to Estimate Both the Product Backlog and Sprint Backlog?

Now that we know what is the product backlog, sprint backlog, and their key differences, let's now address why it is essential to estimate both backlogs. Cannot the team just proceed directly with development, instead of spending time estimating backlogs?

Main Reasons to Estimate the Product Backlog

Product backlog estimation helps the Scrum team to have a set mindset about the whole project. From this perspective, the main reasons to estimate the product backlog are as follows:

Reason 1. Better Guess of Expected Deliveries

Product backlog estimation empowers the team and the product owner to have a better view of how much work they can deliver and by when. It helps the team to know which product backlog items that can deliver by this time. This makes the team well-prepared and also keeps them focused because they know the end goal of all their efforts.

Reason 2. Better Prioritization

Not all product backlog items are deemed important for the project's success. Similarly, there are a few items that should be focused on first, such as bug fixes, key features for the minimum viable product (MVP), etc. So, estimation of product backlog helps product owners to make better prioritization decisions. They can prioritize based on the benefits of the items, the completion time, customer demands, costs, etc.

Reason 3. Fewer Surprises

Estimation of the product backlog is carried out in a proper estimation session where the team sits together and discusses the items one by one. This means that all the major complications of the items are pinpointed in that discussion. This leads to a well-knowledged team, eventually leading to fewer surprises when the development begins.

Main Reasons to Estimate the Sprint Backlog

There is another misconception found in Scrum teams that if they have estimated product backlog, then why should they estimate the sprint backlog when it is just the subset of the product backlog. So, the following are the key reasons that highlight the importance of estimating sprint backlog:

Reason 1. Better Understanding of the Current Sprint

When team members gather to estimate the sprint backlog, they are basically finalizing and prioritizing the work they have to complete in the current sprint. They pinpoint the challenges associated with the work, which helps them better assess the workload. Moreover, estimating sprint backlog also increases the chances that the team will finish all the tasks by the deadline.

Reason 2. Better Work Coordination

Estimating sprint backlog in the sprint planning meeting helps the team to better distribute work to the team members. For instance, the current sprint might have more work for the designer. So, an estimated sprint backlog helps to identify this issue and lets the team make an appropriate plan so that the workload for the designer can be managed.

Why Product Backlog and Sprint Backlog Should be Estimated as Separate Units?

There is no doubt that estimating product backlog and sprint backlog brings a lot of benefits for Scrum teams. Therefore, there is no denial of their estimation. Now the question is why do Scrum teams should estimate product backlog and sprint backlog as separate units? The answer is very well explained by Mike Cohn in his blog post. Let's discuss it thoroughly to clear your concepts around it.

Product backlog and sprint backlog have different purposes to fulfill, so doing their estimate as one unit does not fulfill the objective. Product backlog involves a large items list, so it is crucial that the team completes the estimation much faster.

Consider that the manager requests the team to do estimates of 30 items of product backlog in the form of user stories using Planning Poker or Async Poker estimation technique. Maybe the intention of the manager is to know if additional members are required to be hired for the project or the manager wants to know the expected completion date of the project.

When the team begins the estimates and do estimates of product backlog and sprint backlog as one unit, then the team will be separating user stories into tasks and then estimate them one by one. This will eventually result in huge time wastage on just doing estimations. For example, if it takes 12 minutes on average to discuss and estimate one user story, then 30 stories would take 360 minutes or 6 hours of the team.

However, if the team just emphasizes product backlog estimation, then neither they will split the stories into tasks nor the discussions will be that large. So, it will roughly take 3-4 minutes to estimate one story, which means a total of around 1.25 hours of the team, thereby saving significant time.

It is recommended to do product backlog estimation in the form of story points using Planning Poker or Async Poker technique, while the sprint backlog estimation in the form of hours. Story points are a must easier way for the team to reach a consensus and have a better understanding of the items. However, story points are not ideal during sprint backlog estimation because the target in it is to find how much work the sprint can handle. That's why hours-based estimation works best for it.

In a nutshell, product backlog and sprint backlog are two different units meant for two different purposes. Their estimation technique is also different, so it is highly inefficient to estimate them as one unit.

What's the Ideal Time to Estimate the Product Backlog?

The best time to estimate the sprint backlog is during the spring planning meeting when the sprint backlog is prepared. But there is no such exact time for estimating the product backlog. So, we cannot narrate the ideal time for estimating product backlog, but there are two times at which estimating product backlog is recommended.

The first time the team should estimate product backlog is during the quarterly meeting conducted by the product owners. The target of this meeting is mostly to pinpoint those user stories that are meant to achieve higher goals beyond just one sprint. So, it could take a couple of hours to identify those user stories (product backlog items) and then just 1-2 hours to estimate them.

The second time the team should estimate product backlog is before or after sprint only in case new items are added to the product backlog. This estimation meeting can be carried out anytime or during product backlog refinement meetings or right after daily scrum. However, it is recommended to hold this estimation meeting a bit later in the sprint so that most of the new user stories are identified.

Cannot You Estimate Product Backlog Items in Sprint Planning?

There is a very interesting question that if a team is estimating the sprint backlog in the sprint planning meeting, then why not first estimate the product backlog and then the sprint backlog? There are two major reasons why a team should not estimate product backlog items in sprint planning, as listed below:

Reason 1. Difficulty for Product Owner to Prioritize

If a team estimates product backlog in sprint planning, then it is way too late for the product owner to prioritize items. The product owner needs estimation of product backlog before sprint planning for accurate prioritization of backlog items. Afterward, when the team goes for sprint planning, they will have a pre-prepared estimated product backlog that they can use for estimating sprint backlog.

Reason 2. Longer Estimation Session

If product backlog estimation is also on the agenda of the sprint planning session, then it will prolong the estimation session, resulting in more stress and reduced accuracy. It is because the spring planning will become more detailed and focused, making it take longer to estimate each item of the product backlog.

In a nutshell, it is recommended to estimate product backlog items outside of sprint planning so that the team and product owner are well-educated about the backlog items beforehand.

Who Should Estimate Product and Sprint Backlog?

Product backlog items are basically the summary of the whole project that the team is going to focus on for the next few months. So, when it comes to estimating product backlog, all the teams that are going to be part of the project should be part of the meeting. This could include developers, QA, designers, etc. Moreover, scrum master, product owner, and key stakeholders should also be part of the estimation.

Estimation of sprint backlog is carried out during sprint planning and it is just the small subset of the product backlog, so the whole team's participation is not required. Only the ones that are going to work on the current Sprint are enough to do estimates.

Final Words

Undoubtedly, estimation of the product backlog and sprint backlog bring fruitful outcomes for the Scrum teams. Estimation of product backlog lets the team get a clear picture of the product backlog items the team is going to work on, while sprint backlog gives a clear view of the tasks of the current sprint. Moreover, we can conclude from the above discussion that estimation of the product backlog and sprint backlog should be done separately, where the product backlog should be estimated first or late enough during a sprint so that most new user stories are also identified.

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