Cumulative flow diagram: how to read and build one

A CFD is a stacked area chart. Time runs along the bottom, one point per day. The height is a count of cards. Each coloured band is a column of the board, stacked in order, with Done at the bottom and the first column at the top.

It's cumulative because Done only grows: every finished card stays counted. So the bottom band rises steadily for a team that's finishing work, and the top edge of the chart shows every card that has ever reached the board.

• Vertical distance between bands is how many cards are in a stage on a given day. The distance from the top of Done to the top of In Progress, for example, is the work in progress that day.
• Horizontal distance between bands is roughly how long cards take to get from one stage to another. From the top of In Progress across to the top of Done is an approximate average cycle time.
• The slope of the Done band is throughput: how many cards finish per day. Steeper means faster.

• Parallel bands that rise steadily. Healthy flow: work arrives and finishes at a similar rate.
• A band getting wider. Work is piling up in that stage. The column after it is usually the bottleneck.
• A flat Done band. Nothing is finishing. Check what's stuck.
• The top band rising faster than Done. Work is arriving faster than it's finished. The queue will keep growing until something changes.
• Steps instead of slopes. Work moves in batches, like a release every 2 weeks. Normal for some teams, but it lengthens cycle time.

1. Once a day, at the same time, count the cards in each column of the board. Count every card that has ever reached Done, including archived ones.
2. Record the counts in a spreadsheet: one row per day, one column per board column.
3. Insert a stacked area chart, with Done as the bottom series and the first column as the top.
4. Give it at least 2 weeks of data before reading much into it.

Columns that change partway through, like a new review stage, break the chart's history. Note the date of any change to the board.

• It shows averages, not individual cards. One card stuck for a month hides inside a healthy-looking band. Look at the oldest cards on the board as well.
• It counts cards, not effort. 10 small cards and 10 large ones look the same.
• It can't say why. A widening band shows where work piles up, not what's causing it. That needs a conversation.

craaft doesn't draw a cumulative flow diagram. Each column on a board shows its card count, so recording the daily numbers takes a minute, and every card's activity records each move between columns with its date.

An agent connected over MCP can read a board's activity and work out the daily counts for a CFD, or the cycle times behind it. To act on what the chart shows, put a WIP limit on the column where work piles up.