What Is PDCA Cycle (Plan-Do-Check-Act)?
Also known as: PDCA, Deming cycle, Shewhart cycle, plan do check act, PDSA
Definition
The PDCA cycle is a four-step improvement loop: Plan a change, Do it on a small scale, Check the results against the plan, and Act to standardize the change or adjust and repeat. It is also called the Deming or Shewhart cycle.
PDCA Cycle (Plan-Do-Check-Act) Explained
PDCA was developed from Walter Shewhart's work and popularized by W. Edwards Deming. Plan defines the problem, analyzes the cause and sets a measurable target and countermeasure. Do implements the change on a small scale or in a pilot. Check compares measured results with the target and asks what was learned. Act standardizes the change if it worked, or revises the plan and starts again.
Deming later preferred PDSA, with Study replacing Check, to emphasize learning from results rather than simple inspection. In practice the two names are used interchangeably in lean and quality settings.
PDCA underlies many other methods. A3 problem solving is a PDCA story on one sheet. Kaizen events run a compressed PDCA. ISO 9001 and AS9100 build the same loop into their management system requirements. DMAIC is a more structured relative used in Six Sigma projects.
The Check step is where ERP data is most useful. Before and after measures of cycle time, scrap, on-time delivery or cost from ERP and quality records give an objective result. The Act step often means updating the routing, bill of materials, inspection plan or work instruction so the new method is the system default.
Why It Matters
- Provides a simple, repeatable structure for any improvement or corrective action.
- Pilots limit risk before changes are rolled out plant-wide.
- Forces a measured check, so improvements are verified rather than assumed.
- Aligns with quality management system continual improvement requirements.
In Practice
A plant sees repeat late shipments from one work center. Plan: target a 15 percent reduction in queue time with a revised dispatch rule. Do: trial it on one shift for two weeks. Check: ERP operation history shows queue time dropped on that shift. Act: adopt the rule on all shifts and update the scheduling procedure.
Frequently Asked Questions
What does PDCA stand for?
Plan, Do, Check, Act.
What is the difference between PDCA and PDSA?
PDSA replaces Check with Study to stress learning from the results. The structure is otherwise the same.
How is PDCA different from DMAIC?
PDCA is a general four-step loop. DMAIC is a five-phase Six Sigma method with heavier statistical analysis, suited to complex or data-rich problems.
Where does PDCA appear in ISO 9001?
ISO 9001 builds the cycle into its process approach, covering planning, operation, performance evaluation and improvement.
Related Terms
Kaizen (Continuous Improvement)
Kaizen is the Japanese term for continuous improvement: a habit of making many small, frequent changes to processes, led by the people who do the work, rather than relying on occasional large projects or one-off redesigns.
DMAIC (Define, Measure, Analyze, Improve, Control)
DMAIC is the five-phase Six Sigma method for improving an existing process: Define the problem, Measure current performance, Analyze root causes, Improve with verified solutions, and Control the gains so they last.
5 Whys (Root Cause Analysis)
The 5 Whys is a root cause analysis technique that asks why a problem happened, then asks why again of each answer, typically about five times, until a cause is reached that can be fixed and prevented from recurring.
Six Sigma
Six Sigma is a data-driven improvement methodology that reduces process variation and defects using statistical analysis, targeting a capability level of 3.4 defects per million opportunities, typically executed through the five-phase DMAIC cycle.
FMEA (Failure Mode and Effects Analysis)
FMEA (Failure Mode and Effects Analysis) is a structured risk assessment that identifies how a product or process can fail, the effects and causes of each failure, and existing controls, then prioritizes actions to prevent the highest-risk failures.
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