What are Estimates? #

“Estimates” or estimations are commonly used terms during sprint planning or project planning exercises. They define the size of the work needed to achieve certain acceptance criteria or milestones in a project. It is essential to be explicit about the units of estimation being used—whether story points or hours—as this can cause confusion (e.g., 8 story points is not the same as 8 hours).

What are Story Points and How Are They Different from Hours? #

Story points are units of measure for expressing an estimate of the overall effort required to fully implement a product backlog item or any other piece of work. Teams assign story points relative to work complexity, the amount of work, and risk or uncertainty.

There are several reasons to use story points over hours. Dates don’t account for non-project-related work that inevitably creeps into our days, such as emails, meetings, and interviews. Moreover, dates have an emotional attachment to them, whereas relative estimation removes this emotional attachment. Each team will estimate work on a slightly different scale, which means their velocity (measured in points) will naturally be different, making it impossible to play politics using velocity as a weapon. Once a team agrees on the relative effort of each story point value, points can be assigned quickly without much debate. Additionally, story points reward team members for solving problems based on difficulty, not time spent, keeping the focus on shipping value rather than merely spending time.

Developers with varying degrees of experience can still agree on the same story point for a task, but if they both had to do the same task, each would spend a different number of hours. This understanding is very important. While story points are not perfect, they do mitigate some inherent issues with static hour-based estimates, allowing for a more flexible and fair estimation process.

Benefits of Using Story Points #

Using story points for estimation has several benefits. It reduces the emotional attachment to deadlines by removing the direct association with dates. This is particularly important as dates often fail to account for non-project-related tasks such as emails, meetings, and interviews. Story points promote a focus on the complexity and effort required rather than the time it takes, which aligns well with Agile principles of delivering value. This method also allows teams to quickly assign points once they have agreed on the relative effort of each story point, facilitating a more efficient planning process.

Additionally, because each team estimates on a different scale, their velocity will naturally vary, making it impossible to compare velocities across teams directly. This prevents the misuse of velocity as a metric for performance comparison. Furthermore, story points encourage team members to solve problems based on difficulty rather than the time spent, maintaining the focus on delivering value.

Addressing Variability in Estimates #

It is important to note that while developers with varying experience levels can agree on the same story point for a task, the actual hours spent by each developer may differ. This variability underscores the value of using story points, as they provide a more standardized measure of effort that accounts for differences in individual work pace and experience. Story points are not without their flaws, but they address many issues associated with static hour-based estimates, offering a more adaptable and equitable approach to project planning and execution.