QualityLean

5 Whys

A root cause technique where you ask "why?" repeatedly until you reach the fundamental cause of a problem.

The 5 Whys is a simple, structured questioning technique: starting from a problem statement, you ask "why did this happen?" and then keep asking "why?" of each answer — typically about five times — until you reach a root cause you can actually act on rather than a symptom.

Developed within the Toyota Production System, it is deliberately low-tech. Its power depends entirely on honesty and going to the gemba to verify each answer with facts. It pairs well with a fishbone diagram for problems with multiple contributing causes.

Go Deeper
Root Cause Analysis framework→5 Whys Worksheet→
Related Terms
Root Cause Corrective Action
The disciplined process of finding a problem's fundamental cause and implementing a permanent fix.
Fishbone Diagram
A cause-and-effect diagram that organizes potential causes of a problem into categories shaped like a fish skeleton.
8D
A structured eight-step problem-solving and corrective-action method, widely used in automotive supplier quality.
A3 Thinking
A structured problem-solving approach that fits the whole problem, analysis, and countermeasures on a single A3-size sheet.
Gemba
The actual place where work happens — the shop floor — where leaders go to observe reality firsthand.

Put 5 Whys into practice

SymplProcess turns these concepts into working models, calculators, and templates your whole team can use — no spreadsheets required.

Open the App → Try the Process Modeler
← Browse all glossary terms