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What Is A Scrum Burndown? This Might Surprise You!

The "Scrum Burndown Chart" (See more Burndown Chart in Scrum) is a visual measurement tool that shows the remaining work after each Sprint against the projected rate of completion for the current project release.

Its purpose is to enable the Scrum Product Owner, the Scrum Team, and other stakeholders to control the progress of the project. So the Scrum Team can work toward delivering the requested software solution within the desired timeline.

Simple Scrum Burndown Chart

The speed/rate of progress of a Scrum Team is called "Velocity". It expresses the total number of story points completed that the Scrum Team delivers per Sprint (Iteration).

An essential rule to assess and calculate the Velocity is that; Only entirely completed user stories that precisely fulfill the product’s Definition of Done (DoD) are counted. The velocity calculation shouldn't take partially completed user stories into account. (For instance, coding of a user story is done, but its tests are still missing)

After a few Sprints, observed Velocity gives the team an initial basis for forecasting. Its usefulness depends on stable conditions and must be inspected as more evidence emerges. That helps the Scrum Product Owner to predict the throughput of the Scrum Team better, and he or she can foresee what user stories the Scrum Team can deliver in a given Sprint. That would enable the Scrum Product Owner to plan software releases more accurately, with fewer surprises towards business clients and end-users.

As a simple example: Let's assume the Velocity of your Scrum Team is 50 story points per Sprint. And the total amount of remaining work has been estimated as 300 story points. Then assuming stable Velocity and unchanged scope, you can forecast that you need 6 Sprints to deliver all of the remaining user stories from the Product Backlog.

However, in reality, the user stories in the Scrum Product Backlog will change over the course of the project. New stories are added, and other stories are modified or even deleted.

In the Simple Burndown Chart, the Velocity of the Scrum Team and the change of the scope cannot be visualized accurately. To increase this lost accuracy and visibility, Scrum Teams use another type of diagram, which we call "Extended Burndown Chart".

Extended Burndown Chart uses a bar chart instead of a line diagram. The size of each bar represents the total amount of remaining work, measured in story points, at the beginning of each sprint. The Velocity of the Scrum Team is subtracted from the top bar, while changes of the Product Backlog are presented at the bottom of the bar.

Extended Burndown Chart Separating Velocity and Scope Changes

To get even more accurate results with the Burndown Chart, we can also take the rate of changes in total work into account. We call this more precise model "Extended Burndown Chart With Prediction”. However, we have to be careful when using this model. This illustration assumes that changes to the Product Backlog are relatively large at the beginning and decline toward zero near the end. Actual scope can behave differently, so the forecast must be updated when that assumption no longer fits.

Extended Burndown Chart with Prediction