5 Whys Analysis Tool
Ask why five times to move past symptoms and reach the real cause of a problem. Fill in the chain below, then share it as a link or export it as a PDF. No signup, no data leaves your browser.
Describe the problem clearly and specifically. A precise problem statement makes every following step sharper.
What is the 5 Whys method?
The 5 Whys is a root cause analysis technique developed at Toyota. You start with a clear problem statement and ask why it happened. You take the answer and ask why again, repeating around five times until you reach a cause that, if fixed, would stop the problem from coming back.
The number five is a guideline, not a rule. Some problems reveal their root cause in three steps, others take seven. The goal is to stop at a true cause you can act on, not a symptom and not a person to blame.
How to use this tool
State the problem
Write down what actually happened, with enough detail that someone else would recognise it.
Ask the first why
Why did this problem occur? Base the answer on evidence, not assumptions.
Keep asking why
Take each answer and ask why again. Each step should follow logically from the one above it.
Reach the root cause
Stop when you reach a cause that, if removed, prevents the problem from recurring.
Share and act
Copy the chain into your ticket, share the link with your team, or export a PDF, then assign a corrective action.
For the wider background on when to use this method and how it sits alongside the others, read our full guide to the 5 Whys method and root cause analysis.
A worked example from a production line
Here is a complete chain for a common class of problem. Every answer is something you could verify with a record, a measurement, or a look at the machine. That is the difference between an analysis and a guess.
Problem: The final assembly line stopped for 40 minutes during the morning shift.
Why did the line stop?
The torque tool at station 7 shut down mid-cycle and locked the station.
Why did the torque tool shut down?
Its internal temperature went past the cut-off limit.
Why did it overheat?
The cooling air line to the tool was carrying about half its normal flow.
Why was the air line throttled?
A filter in the supply line was clogged and had never been changed.
Why was the filter never changed?
The filter is on no maintenance plan. It arrived with a line modification in 2024 and was never added to the schedule.
Root cause: Parts added during a line modification do not automatically enter the preventive maintenance plan. That gap will cause more failures than this one.
Corrective action: Change the handover after a modification so every added component is registered in the maintenance plan before the line is released. Then audit the last two years of modifications for other unregistered parts.
Stopping after the second why would have produced "replace the tool". The line would have stopped again.
Five ways a 5 Whys goes wrong
Failed analyses fail in the same handful of ways. Check your chain against these before you act on it.
The chain ends at a person
If the last answer names someone rather than a system, keep going. Ask why the system allowed it, and what would have caught the mistake.
The answers are assumptions
Every answer needs evidence: a log entry, a measurement, a photo, a witness. Mark any step you cannot verify, then go and check it.
The problem statement is vague
"Quality issues in packaging" has no single cause. "Twelve cartons on line 3 were sealed off-centre on 4 March" does.
One branch when there are several
Some problems have two or three contributing causes. Run a separate chain for each, or spread the possibilities out in an Ishikawa diagram first and take the strongest branch into a 5 Whys.
Stopping at five out of habit
Five is a rule of thumb. Stop when you reach a cause you can remove and whose removal prevents recurrence. Sometimes that is three steps, sometimes seven.
Questions about the 5 Whys
Why five whys and not three or ten?
Five is an average, not a target. Taiichi Ohno at Toyota used the number as a reminder not to stop at the first plausible answer. Stop when removing the cause would keep the problem from coming back.
When should I not use the 5 Whys?
When a problem has several independent causes, or when you need statistical proof of a relationship. Spread the possible causes out in an Ishikawa diagram first, and use a designed experiment or data analysis when you have to prove which cause dominates.
How does the 5 Whys fit into an 8D report?
It is normally step D4, the root cause analysis. The 8D wraps containment, corrective action, verification and prevention around it. If a customer asked you for an 8D, the 5 Whys chain sits in the middle of it.
Who should be in the room?
The people who do the work and saw the problem, plus someone who can approve a change to the process. Three to five people is usually enough. A chain built without the operator rarely survives contact with the shop floor.
How do I document the result?
Keep the whole chain, not just the root cause. The chain is the reasoning, and the next person needs it to judge whether the conclusion still holds. Copy it into your ticket, or use the export and link buttons above.
Is this tool really free, and where does my data go?
It is free and needs no account. Everything you type stays in your browser. The shareable link encodes the analysis in the URL itself, so nothing is stored on our servers.
Finding the root cause is only half the job
A cause on a printout changes nothing. Mobile2b turns findings into assigned corrective actions and tracks them to closure across your plant, on premise if you need it.
See how it works