What is a Cumulative Flow Diagram?

What is Cumulative Flow Diagram?

A Cumulative Flow Diagram (CFD) is a visual metric used in Kanban to analyze the work you’ve done. The diagram highlights the amount of work started, of work in progress, and the work completed. It represents data in an area graph. Cumulative Flow will show you the total volume of work for any of the process stages. If you have 3 stages: to do, in progress and done, then your CFD will have three areas.

Jumps and flat lines on the Cumulative Flow Diagram instantly show you where any constraints or bottlenecks are occurring, while smoothly rising lines on the graph ensure accuracy in your ability to predict when work will be completed.

There are many ways to draw data from a Kanban solution, but the Cumulative Flow Diagram is the overall best way to track progress and estimate process health.

Who needs the Cumulative Flow Diagram?

How many times have you been dragged into your boss’ office with a demand to state when his favourite project will be done? You’d go ahead explaining that you don’t have the data on hand, and if he gives you a few hours you may be able to provide an answer… Would it not be great to simply show him a graph with all that information in an easy, objective, all-inclusive way? A CFD can easily be used as such.

A CFD layout

A Cumulative Flow Diagram consists of a colored chart on an x and y-axis. The x-axis represents the elapsed time, while the y-axis shows the number of cards or work items. This way, the CFD shows the total volume of each stage in your process. For example, a software company may have 4 work stages:

  • 1 – Customer ready request (green),
  • 2 – Requirements drawn (dark blue),
  • 3 – Development and testing done (yellow),
  • 4 – Request delivered to the customer (pink).

This would mean that the company would have 4 colored areas to their Cumulative Flow graph, one area per each of the stages, as shown on the diagram below.

Cumulative Flow Diagram

We can see from the diagram that in January, there were 20 customer requests (green area), depicted by the letter A. Towards the end of January, the team was working on 20 requirements specifications (dark blue area) as depicted by the letter B. Around the end of February, 20 items had been completed regarding the requirements specification phase, and 20 items were being worked on in development and test (yellow area), depicted by the letter C. At the beginning of April, we can see that the team finally completed 20 items (pink area). So, the total cycle time for 20 items can be seen to be 3 months.

The project manager could send this directly to their boss, or simply have it available in a portal where the boss and stakeholders could pull this information for themselves, at any time.

Use a Cumulative Flow Diagram to predict the future

There is a lot more that a CFD can do for your business! You could look at the smoothness of the lines to determine the predictability or efficacy of a process step. Team members could see that in March, there was a spike in customers’ demand for work, and this led to the green area increasing in velocity over the other work states. Understanding the processes that a team is part of helps them to better respond to changing conditions.

Although there is so much information to glean from the diagram, the best thing to use it for is predicting when an item is going to get completed. One of the most important reasons for the success of any business is the alignment of their estimates with reality. Using data from the Cumulative Flow Diagram, a business can determine when items are going to get completed, and the longer the period of time that data was gathered over, the more reliable their predictions. If a company is able to use 7 months of data gathered by their Kanban Software, as in this example, their chance of success greatly increases, with hardly any analytical work needing to be done!