What is a scrum burndown chart and why is it so important in Scrum?
Scrum teams hate unnecessary bureaucracy. They don’t like meetings, they don’t like endless paperwork. They just want to focus on getting the job done. However, one report they will happily produce is the scrum burndown chart. Which might make you think that the burndown chart must be a really good report, and you’d be right.
Why scrum burndown charts?
A scrum burndown chart is very simple. It plots time remaining against work remaining. The idea is to see, at a glance, when you’re likely to be complete. Using an example project that consists of 250 story points and 20 iterations, a likely burndown chart would look like this:
The vertical axis indicates work remaining (titled Story Points in this image) and the horizontal axis indicates time (titled Iterations in this image). If you drew an imaginary line between the start point and through the average of the plotted points, you’d get your projected end point. If you do that on the graph above, you’ll see that we won’t be completed by iteration 20. In fact, the end point doesn’t appear on the graph!
As you can imagine, the perfect graph goes from top left to bottom right in a straight line. This assumes that top left is the start point and that bottom right is the end point. In this graph, top left is iteration 0 with 250 story points. Bottom right is iteration 20 with 0 story points. In the graph below, I’ve drawn the ideal line in blue.
It’s clear that, almost from the start, the team were missing their target. From iteration 8, they were really going off course. By iteration 12, things had got as bad as they could get but on iteration 13, a lot of work was completed. The beauty of the graph is that my narrative is unnecessary. The graph makes the true position totally transparent to anyone.
Scrum burndown chart = clarity
Creating and maintaining a burndown chart is simplicity itself. You’ll often see them hand drawn and stuck up on the wall in the daily scrum meeting place. It provides a wealth of information in a concise, transparent and easily understood way. No wonder scrum teams love them!
One final thought …
If there’s one thing that the basic scrum burndown chart doesn’t show well, it’s changes in requirements. Imagine the scenario: Your customer, flush with the success of your Scrum project, has decided to add in extra user stories. After iteration 8, when the development team had completed 10 user points, the customer added in some new user stories that also totalled 10 story points. Net effect on the burndown chart? No progress indicated, as shown above.
It won’t surprise you to know that this is a common situation in Scrum projects and there’s a variation on the burndown chart that handles it. It’s called the burn-up chart.