Cumulative Flow Diagram (CMD)
The Cumulative Flow Diagram is Kanban's calling card, allowing you to look at the production process at a glance and understand its overall status.
On the one hand, you can find standard project information on the graph - how much work has been done, how many tasks remain, and the project pace. These are the basic metrics. On the other hand, by understanding the nature of the graph, you will be able to see all the types of problems the team may be facing. This is where the real usefulness of the graph lies.
How to read and understand the Cumulative Flow Diagram
The diagram shows the number of tasks in each stage of the production process on a given date.
The horizontal X-axis is the time axis.
The vertical Y-axis shows the number of tasks in each stage of the process on the corresponding day.
The coloured areas on the graph show how the number of tasks in each process step changes over time.
The bottom area (in orange) normally shows the number of tasks completed. It is natural to expect that it will grow continuously.
The upper area (blue) - shows the number of tasks planned. In the chart above, its upper boundary remains unchanged, i.e. no new tasks are added to the queue. But you may have a different situation.
Intermediate areas - show the stages of work between "Scheduled" and "Done". It can be a single "In progress" stage or several stages, as shown in the figure above.
Let's explain with an example
Let's assume you have 4 major steps on your board: To Do, Development, Testing and Done.
The To Do column is considered the commitment point and the Done column is where the completed tasks go.
The Development column is split into 2 parts (subcolumns), but this does not affect the display on the CFD.
The CFD could then look as follows
The orange area on the graph shows the number of tasks completed.
The green and grey areas show the number of tasks in development and testing, and their combined width shows the amount of work being done simultaneously. If we notice later on that these areas are getting wider, and the orange area is not growing, it means there are problems in the process.
The blue area is the number of tasks in the queue. In this case, we can note the change in the scope of work - the change in the upper boundary of the blue area. That is, new tasks have been added to the queue during the sprint.
We can also see the delivery time. How many days a certain number of tasks have reached from the "Taken to Work" stage to the "Done" stage. In this example, the average time needed to complete a task is 9 days.
We can also get a rough estimate of when the project is finished. You can do this by activating the "Show Trend" function. Trend lines will be drawn for the upper and lower zones on the chart. If the lines cross in the future, a pop-up window will show the date of the crossing. This is the projected completion date for all tasks. Of course, it will change if the number of tasks or delivery time changes.
How to interpret information from the Cumulative Flow Diagram
Your graph may vary considerably from the one shown above. This depends on the number of steps in the work and on the quality of your workflow.
The main thing to remember is that each area on the graph shows how long the tasks have been in each stage.
Let's look at some examples:
In this graph we see a large amount of unfinished work in the in progress phase. The grey area increases over time, with new tasks moving into, but not being sent further on to the same extent:
In the following graph we can see the stoppage in activity. Note the grey, green and orange area between 12.07 and 17.07 - the areas do not move upwards. This means that there has either been no work at all or no progress has been made:
