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The four phases
| Phase | Key question | Typical activities |
|---|---|---|
| Plan | What do we want to achieve, and how? | Describe the problem or goal, analyse causes, define actions and measures |
| Do | Are we implementing the plan? | Implement the action, often first on a small scale or as a pilot |
| Check | Did it work? | Measure results, compare with the goal, understand deviations |
| Act | What follows? | If successful, standardise; otherwise adjust and start a new cycle |
The cycle never ends. What becomes the new standard in “Act” is the starting point for the next round. This creates gradual improvement instead of one-off projects.
PDCA in ISO standards
The shared structure of management system standards mirrors the cycle: clauses 4 to 6 describe planning, clauses 7 and 8 support and operation, clause 9 performance evaluation and clause 10 improvement. Anyone implementing ISO 9001, ISO 14001 or ISO 27001 therefore works according to PDCA, whether they call it that or not.
The cycle also appears on a small scale, for example in a corrective action: analyse the cause and plan the action, implement it, check effectiveness, carry the result into instructions.
An example
- 1
Plan
A shipping team finds that 4% of deliveries are picked wrongly. Goal: below 1% within three months. Cause: similar item numbers are stored next to each other. Action: re-sort storage locations and introduce scanner checks.
- 2
Do
The action is first implemented in one warehouse zone.
- 3
Check
After six weeks, the error rate in that zone is 0.8%, in the others still 4%.
- 4
Act
The re-sorting is rolled out to all zones, the work instruction updated and the team trained.
Common mistakes
- Starting with “Do” without defining a goal and measure. Then “Check” is impossible.
- Stopping after “Do” because the action is done. Whether it worked remains open.
- Forgetting “Act”: the improvement is not carried into instructions and gets lost again.
PDCA in docxpert
In CAPA management, the flow from root cause analysis through actions to the effectiveness check mirrors the cycle. You carry the result into controlled documents through change control and use read acknowledgement or training to evidence that the team knows the new version.
Frequently asked questions
Is PDCA the same as continual improvement?
Not quite. [Continual improvement](content:term-continual-improvement) is the mindset of improving all the time; PDCA is the method that structures each individual improvement step.
What is the difference between PDCA and PDSA?
Deming later spoke of “Study” instead of “Check” to stress that results should be understood, not just inspected. The flow is the same.
Does ISO 9001 explicitly require PDCA?
The standard describes the cycle in its introduction as the basis of the process approach. It does not require any particular documentation of the cycle.
How long does a PDCA cycle take?
It depends on the topic: from a few days for a small process change to a year for strategic objectives reviewed in management review.