A burndown chart is a graphical representation of work left to do versus time. The outstanding work is often on the vertical axis, with time along the horizontal.
It is useful for predicting when all of the work will be completed.
What is Burn up Chart?
A burn-up chart tracks progress towards a project’s completion. In the simplest form of burn up chart, there are two lines on the chart:
A total work line (the project scope line)
A work completed line
What is a Sprint Burndown chart?
The Sprint Burndown Chart is a visual measurement tool that shows the completed work per day against the projected rate of completion for the current sprint. It provides transparency about the current performance (burndown rate) and allows easy estimation if the Sprint Goal can be reached in time or if the team has to find additional measures to speed-up completion of the remaining activities. The rate of progress of a Scrum Team is called "velocity". It expresses the amount of work in story points completed per sprint. An import rule for calculating the velocity is that only stories that are completed at the end of the sprint are counted. Counting partially finished work (e.g. coding only - test missing) is strictly forbidden.
It helps the user to understand how quickly your team has completed tasks, and predict when your team will achieve the goal or goals of the sprint.
What does a Burndown chart show?
It is the sum of efforts in hours of all the user-stories, tickets, and issues, basically it’s the total number of works in hours to which the team is committed to.
Amount of work Remaining or Effort Remaining
This is what burn down shows and this is how this graph get its name, in literal meaning it is the “effort burndown chart”. The Team will burndown some effort each day so that on last day of sprint or release there is no work effort remains.
Since team need to calculate and carefully work on the commit item each day, so that is the reason total days of commitment of work are shown in graph. This is the total working days in a sprint (excluding holidays, weekend, etc.). This is actually your sprint duration.
The ideal effort is drawn as a guide for a team, its drawn by calculating the exact amount of effort remaining which team need to burndown. That is the reason you see a very straight line from the top of Y-axis to X-axis, which is the last day of your sprint.
Effort remaining line varies from team to team and day to day. It depends on how much effort remaining is added or reduced each day. If more items (user stories and issues) are added after the sprint started, this show as an upward spike.
The chart can help in answering the following questions:
How good is this team with the planning?
How well is this team executing against the planned stories in a Sprint?
Is this team self-organized and are they working in unison as a "team"?
What improvements can this team make?
How to read Burndown chart
The burn down chart is simple to understand:
X axis for days of the sprint
Y axis for effort (story points or hours or days depending on what you prefer)
Ideal line that visualize expected progress
Real line visualizing the current progress
At the start of an iteration the team estimates the work for all the tasks it commits to. The sum of all the hours estimated in story points for all the tasks is the starting point for the graph. Every day as the team members work on tasks, the remaining work plotted on the chart should also reduce. The chart should be updated each day and the graph should ideally displays a downward trend. What makes the chart an effective reporting tool is that it shows the team's progress towards the Sprint Goal, not in terms of time spent but in terms of how much work remains.
Burndown chart samples
The following samples show the team status based upon the Burndown chart.
Type 1: Sprint commitment met A burn-down chart in which sprint commitments are met and progress has been smooth over the sprint.
Type 2: Sprint commitment not met The teams are going at a slower pace and may not be able to complete all the commitments on time. The remaining work then becomes a part of the product backlog and is carried forward to subsequent sprints.
Type 3: Sprint commitment met early before time It shows that we are going at a better rate and may be able to finish earlier. The stories were probably overestimated; therefore, the team finished them earlier.
Advantages of using Burndown charts
Single planning and tracking tool for the team
The team performs task breakdown, updates the estimated effort, and also updates the effort remaining. The entire team drives planning and tracking using the burn-down tool, which is the biggest advantage of using it.
Risk mitigation by daily visibility
The burn-down chart provides daily feedback on effort and schedule, thereby mitigating risks and raising alarms as soon as something goes wrong, rather than waiting till the end.
Communication tool for customer and other stakeholders
Burn-down charts provide visibility of a project’s progress on a daily basis. In the absence of an online tool, burn-down can be physically represented using a whiteboard/chart paper.
Placeholder to track retrospective action items
It is a good practice to include retrospective action items from the previous sprint as "functional requirements" in the task breakdown for the current sprint. This way, the team keeps a focus on those action items and they are tracked as the sprint progresses. Common mistakes while using Burndown charts
If the task is too big, then it will make tracking on a daily basis difficult.
People get confused with the effort spent and the effort remaining. If these are wrongly plotted then the report insight will be inaccurate.
Forgetting to update the remaining time for tasks will lead to incorrect data.