A Cumulative Flow Diagram (CFD) is a measurement tool for tracking and forecasting work. CFDs are typically associated with Kanban, however, it can be used as a measurement tool for any type of work. In its simplest form, a CFD is a set of measures that are presented in a visual form. A simple version of a CFP shows the amount of work that has been completed, how much work is in-progress, and the amount of work still to be done over time.
A simple CFD is shown below:
The simple CFD shows the conversion of stories from backlog items into completed stories that have or could be shipped. Comparing two CFDs (shown below), the first after period two with another CFD after period six shows the trajectory of the work and the accumulation of completed functionality. The CFD drives home the point that the team is delivering work that either was or could have been delivered. Visually even a simple implantation of CFD provides valuable information to the team.
The CFD also acts as a tool to monitor the amount of work-in-process (WIP). The gap between the backlog and completed at any point in time is the WIP. While this is very evident in this simple version later in the week, we will explore more complex versions of the CFD. An example showing how to a CFD to identify WIP is shown below:
In order to highlight how a CFD shows work-in-process, I have shown a CFD with a bulge in the flow of WIP. This pattern is an example of bottleneck (more on bottlenecks when we discuss more complex CFD configurations).
Another typical use of a CFD is to monitor cycle time. Cycle time is a measure of the amount of time a unit of work takes to move from the backlog to complete. The cycle time example:
The cycle time is an excellent metric for forecasting when a project will be completed or when a certain number of stories will be completed.
A third common metric that a CFD provides is throughput. Throughput is the number of stories completed in a time period. The average throughput over a number of periods would be velocity.
Throughput and velocity are predictive metrics that are valuable to help teams predict when they can complete work or whether they are improving their rate of delivery.
The Cumulative Flow Diagram provides teams and organizations with a tool to understand current status, identify bottlenecks and issues, and to forecast completion dates. The CFD is, in Agile parlance, a big information radiator. A team that uses Kanban or Scrumban often replace burn-up and burn-down charts with CFDs because they more closely track the flow of work.
Next: More Complex CFDs