Kanban guide · Flow and metrics
Cumulative Flow Diagram (CFD): How to Read and Use It
A cumulative flow diagram (CFD) shows how many work items are in each stage of your workflow over time. In one chart, it reveals bottlenecks, growing work in progress and changes in delivery rate.
Key takeaways
- A CFD stacks the number of items per stage over time.
- Widening bands show bottlenecks; a flat Done line shows no delivery.
- It approximates WIP, cycle time and throughput visually.
How a CFD is built
Each day, the number of items in each column of the board is recorded. The chart stacks these counts as coloured bands over time, usually with Done at the bottom and the earliest stage at the top. Because items are counted cumulatively, the bands never go down for Done.
Reading the bands
| What you see | What it means |
|---|---|
| Parallel bands of steady width | Stable, healthy flow |
| A band getting wider | Work is piling up in that stage: a bottleneck |
| A band getting thinner | That stage is starved of work |
| Flat top line of Done | Nothing is being finished |
| Steep rise in the top band | Lots of new work arriving |
Approximations from a CFD
- Vertical distance between the top of the in-progress bands and the Done line at a point in time ≈ work in progress.
- Horizontal distance between when items enter progress and when they reach Done ≈ average cycle time.
- Slope of the Done line ≈ throughput.
Using a CFD in reviews
- Look at it in service delivery reviews or retrospectives.
- Find the first band that is widening; that is usually the constraint.
- Check whether WIP limits are being respected.
- Compare before and after process changes.
Free templates for this topic
Frequently asked questions
What is a CFD used for?
To see bottlenecks, WIP trends and delivery rate at a glance.
Can Scrum teams use a CFD?
Yes. A CFD is useful for any team that tracks work through stages.
What is a cumulative flow diagram?
A cumulative flow diagram (CFD) is a stacked area chart showing how many items are in each workflow stage over time. It reveals WIP, bottlenecks and flow at a glance.
How do you read a cumulative flow diagram?
Each coloured band is a stage. The vertical gap between bands shows WIP in that stage, the horizontal distance approximates average cycle time, and the slope of the Done line shows throughput.
What does a widening band mean on a CFD?
Work is entering that stage faster than it leaves, so a queue or bottleneck is forming there.
What does a flat line on a CFD mean?
Nothing is moving through that stage. A flat Done line means nothing has been delivered in that period.
What does a healthy CFD look like?
Bands that rise smoothly and in parallel, with roughly constant thickness, showing stable WIP and steady flow.
How do you create a cumulative flow diagram?
Each day, count the items in each stage plus all items that have passed it, and stack the counts over time. Most digital Kanban tools generate a CFD automatically.
What is the difference between a CFD and a burnup chart?
A burnup shows completed work against total scope. A CFD shows every workflow stage, so it also reveals where work is accumulating.
Can a CFD show cycle time?
It shows approximate average cycle time as the horizontal distance between the line where work starts and the Done line. Use a cycle time scatterplot for item-level detail.
Why does the bottom band of a CFD never go down?
Because it is cumulative: items that reach Done stay counted. Lines only go down if items are removed or moved backwards.