What is a Cumulative Flow Diagram?

What is Cumulative Flow Diagram?

A Cumulative Flow Diagram is a visual metric used in Kanban to analyze the stability of the workflow. Though there are many ways to draw data from a Kanban solution, the CFD, sometimes referred to as the burn-up chart, is the overall best way to track progress and estimate process health, quickly and effortlessly.

Who needs a CFD?

How many times have you been dragged into your superior’s office for an update on when their favourite project will be done? You’d go ahead explaining that you don’t have the data on hand, and if given a few hours you may be able to provide an answer. You can save those few hours and use a Cumulative Flow Diagram for just that - it will provide the answer for you, in an objective and all-inclusive way, as it accumulates all of a project’s tasks and clearly shows tendencies for their completion.
Send the CFD directly to your boss, or simply have it available online for the management, team and stakeholders to pull information from for themselves, at any time.

A CFD layout

The diagram shows data in an area graph, displaying the total volume of work for any of the process stages. If you have 4 stages: to do, in progress, in review and done, then your CFD will have four areas. The x-axis represents the elapsed time, while the y-axis holds the number of work items.

Jumps and flat lines on the Cumulative Flow Diagram instantly show you where any constraints, bottlenecks or lack of any activity are present, while smoothly rising lines suggest constant progress, and ensure your ability to accurately predict when work will be completed.

Example A software development company may have the following 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 means the company will have 4 areas to their Cumulative Flow graph, one area per each of the stages:

Cumulative Flow Diagram

We can see that in January, there were 20 customer requests (green area - letter A). Towards the end of January, the team was working on 20 requirements specifications (dark blue area - 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 - letter C). And at the beginning of April, the team had 20 items completed (pink area). So, their total cycle time for 20 items is 3 months.

Use a Cumulative Flow Diagram to predict the future

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 customer demand for work, leading to the green area increasing in velocity over the other work states. A clear signal, that unless more developers are employed, the cycle time is going to increase significantly. Understanding the processes that a team is part of helps them to better respond to changing conditions.

But 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, you can determine when items are going to get completed, and the longer the period of time that data was gathered over, the more reliable your predictions. Imagine being able to estimate project completion, using several months of data gathered automatically by Kanban software - your chances of success greatly increase, with hardly any analytical work needing to be done on your part!