What is the PDCA cycle?
The PDCA cycle (Plan, Do, Check, Act), also called the Deming cycle or Shewhart cycle, is the basic loop of continuous improvement. Instead of rolling out a change everywhere and hoping, you test it on a small scale, measure what happened and only then make it the new standard. Each turn of the wheel lifts performance a little; many turns add up to large gains.
PDCA is the backbone of lean, Six Sigma and every ISO management system standard. It is also the simplest structured problem-solving method: when a problem is small and the cause is fairly clear, a single PDCA page is often all you need. Bigger problems call for A3, 8D or DMAIC, which are all PDCA with more steps.
The four steps of PDCA
| Step | Key question | Typical content |
|---|---|---|
| Plan | What are we trying to achieve and what change will get us there? | Problem, current data, root cause, measurable goal, planned change and how it will be measured |
| Do | Did we carry out the change as planned? | A small-scale trial, what was done, problems and observations |
| Check | Did it work? | Before and after data compared with the goal, side effects, what was learned |
| Act | What do we do now? | Standardize (procedures, training, controls), adjust and repeat, or abandon |
Most of the effort belongs in Plan. A plan without a root cause tests a guess, and a goal without a number cannot be checked. Use a 5 Whys or fishbone diagram before you choose the change, and decide in advance which data will tell you whether it worked.
PDCA example
The example tackles final leak test failures on an assembly line: 6.2% of valve bodies fail, mostly at the inlet O-ring seat. The team traces the cause to variable insertion depth on a manual press (Plan), fits a hard stop and guide sleeve to one of the two stations for two weeks (Do), and compares the two stations: 2.6% failures with the change against 6.0% without it (Check). The goal of under 3% is met, so the team fits the change to the second station, updates the work instruction and the PFMEA, and plans a second cycle on casting porosity (Act).
Note the built-in comparison: running the change on one station while the other continues as before separates the effect of the change from everything else that varied in those two weeks.
Tips for effective PDCA cycles
- Make the goal measurable. "Improve quality" cannot be checked; "cut failures from 6.2% to under 3% by 31 January" can.
- Test small. One station, one shift or one product first. Small tests are fast, cheap and safe to fail.
- Check with data, not opinion. Use a run chart to see whether a change is real or noise.
- Close the loop in Act. If the change is not written into procedures, training and controls, the gain fades.
- Keep cycling. The output of Act is the input to the next Plan.
Working in healthcare or testing several changes in sequence? Use the PDSA tool, which adds predictions and links cycles on a ramp.
How to use this PDCA Cycle tool
- Describe the improvement. Name the improvement, the owner and the cycle number.
- Plan. Click the Plan quadrant and write a measurable goal, then fill in the problem, current situation, root cause and the planned change below the wheel.
- Set the goal metric. Click the metric strip and enter the baseline, the target and whether lower or higher is better.
- Do. Run the change on a small scale and record what was done and what you observed.
- Check. Enter the result. The tool calculates the improvement and shows whether the target was met.
- Act. Decide to standardize, adjust or abandon, list the actions with owners and due dates, then export the PDCA to PDF or Excel.
Frequently asked questions
What does PDCA stand for?
PDCA stands for Plan, Do, Check, Act. Plan the change and how you will measure it, Do it on a small scale, Check the results against the goal, and Act: standardize the change if it worked, or adjust and run the cycle again.
Who invented the PDCA cycle?
The cycle is based on the work of Walter Shewhart in the 1930s and was popularized in Japan by W. Edwards Deming in the 1950s, which is why it is also called the Deming cycle, Deming wheel or Shewhart cycle. Deming himself later preferred PDSA (Plan, Do, Study, Act).
What is the difference between PDCA and PDSA?
The steps are the same, but PDSA puts more weight on learning: in the Plan step you write predictions, and in the Study step you compare the results with them. PDSA is the standard in healthcare improvement (Model for Improvement). PDCA is the common name in manufacturing and ISO management systems.
Is PDCA required by ISO 9001?
ISO 9001, ISO 14001, ISO 45001 and other ISO management system standards are structured around PDCA. Clauses 4 to 7 broadly cover Plan, clause 8 Do, clause 9 Check and clause 10 Act. The standards do not require a PDCA form, but a documented cycle is good evidence of continual improvement.
How long should a PDCA cycle take?
As short as possible while still producing data. A small change on one line can be tested in days; a process change may need a few weeks to see the effect. Many short cycles beat one long one.
What happens after the Act step?
If the change met the goal, standardize it (procedures, training, controls) so the gain holds, then pick the next problem. If it did not, adjust the plan and run the next cycle. Each cycle starts from the new, higher standard.