How to create a process flow diagram
A process flow diagram is three artefacts under one name. How to choose the level from what the diagram will be used for, hold that level across every box, and break a sub-process out instead of inflating one.
A worked example, stage by stage
Set the grain before row one
The requesting work is finished six rows in: an event, "Raise a requisition with coded specification", then "Funds available in the cost centre?", whose "No" already ends at "Requisition declined or deferred". Neither gate added a screen or a reminder — a diamond carries routing, not work.
One box, six weeks
"Contract or framework in place?" opens the market route: "Yes, call off" reaches "Issue the purchase order to the supplier" directly, while "No, go to market" passes through "Run a sourcing exercise and award" — one box holding an entire tender, because nothing inside it changes the route.
Exceptions at the same grain
Delivery, receipt and the invoice arrive, then three gates in a row. "Goods or service receipt recorded?" sends "Missing, chase it" back to "Record receipt against the purchase order", and only the "Outside tolerance" exit of the match renders yet — the clean route joins later.
Where the loops close
Both remaining loops close here, and neither drops a level. "Exception resolved?" points "Resolved, re-match" back at "Three-way match within tolerance?", and "Raise a retrospective PO and log it" returns to the receipt check. "Still disputed" ends at "Dispute handled under the contract".
Hold it to the last row
Payment posted, the run released, then "Update the vendor and spend records". Four rows in this chart are terminal — a declined requisition, a dispute handed to the contract, an unpaid invoice with no PO, and "Cycle closed and spend reported" — and each is one box rather than a summarised route.
How it works
Name the reader and the use
Write one sentence: who opens this diagram, and what question they open it to answer. Training somebody to perform a job, fixing the handoffs between two teams, and finding where a cycle loses weeks are three different questions, and they produce three differently sized diagrams of the same work.
Fix the grain as a written rule
State it before typing: a box is a unit of work with one owner and one outcome, and nothing inside it changes where the flow goes next. Set a box budget as well — ten to twenty for a procedure, twenty to forty for a process crossing teams — and treat overspend as a levelling error rather than as thoroughness.
Type the steps into rows at that grain
Each row's Box text column is one box, and the diagram builds as the rows do. Work through the process in order and resist expanding the part you happen to know best; the grain rule is what answers whether a step you want to split is really two. The layout is generated, so there is nothing to rearrange afterwards.
Number the routes and label the forks
The Line to column takes the row numbers a step leads to, comma separated where there is more than one, and Line text carries the branch labels in the same order. A number lower than the row it sits on draws a loop back — which is how a diagram says work is repeated without dropping to a finer level.
Fill the lane columns, then break out the bulge
Horizontal lane holds the phase and Vertical lane the owner. Now look for the bulge: the phase carrying three times the boxes of its neighbours. Move its contents into a second chart at the finer level, leave one box behind in the parent named as an outcome, and reference the child from that row's comment.
Test the level on the named reader
Trace the finished chart with the reader from step one and ask one thing of every box: is this the wrong size for them? Expect two answers — one box they want opened, three they never needed. Then write the reader and the level into the chart's title, so the next person proposing a box has a stated scope to argue with.
Frequently asked questions
What is a process flow diagram?
A diagram of the steps and decisions in a process, drawn at one chosen level of detail. The term covers three distinct artefacts: a procedure-level diagram of a single job, a process-level diagram of work crossing several teams, usually in swimlanes, and a chain-level diagram of an end-to-end cycle such as procure-to-pay. They share a notation and answer different questions, which is why the level has to be stated rather than assumed.
Is a process flow diagram the same as a flowchart?
In business use they are interchangeable: a process flow diagram is a flowchart of a process. In chemical and process engineering they are not. There, a process flow diagram is a specific engineering deliverable showing equipment, streams, flow rates and major control loops, standardised by ISO 10628, and the activity diagram most people are after would be called a process flowchart or a process map. Establish which of the two is being asked for before drawing anything.
How do I break a process flow diagram into sub-processes?
Leave one box in the parent and let the child own the level below it. "Run a sourcing exercise and award" is the seam in the example: the parent keeps it as one box whose label ends in the outcome the next arrow depends on — an award — and the child chart begins with the event that box receives and ends in exactly that outcome. That makes the boundary testable: read the child's last row and it must state what the parent box promised. Nothing is drawn twice, and each diagram holds one level.
Which level of process flow diagram should I draw first?
The level that matches the problem in front of you, which is usually the process level that crosses teams. Handoffs between functions are where work stalls, and that level is the only one which shows them. Draw the chain level when the question is where a whole cycle loses its weeks, and the procedure level only when somebody has to be trained on a specific job. Producing all three up front gives you three diagrams that will disagree with each other within a quarter.