5 Whys

Getting to the Root of a Problem Quickly

5 Whys - Getting to the Root of a Problem Quickly

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Simply asking "Why?" can get to the root of a problem.

Have you ever had a problem that refused to go away? No matter what you did, sooner or later it would return, perhaps in another form.

Stubborn and recurrent problems are often symptoms of deeper issues. "Quick fixes" may seem convenient, but they often solve only the surface issues and waste resources that could otherwise be used to tackle the real cause.

In this article, we look at 5 Whys – a simple but powerful tool for cutting quickly through the outward symptoms of a problem to reveal its underlying causes, so that you can deal with it once and for all.

Origins of 5 Whys

Sakichi Toyoda, one of the fathers of the Japanese industrial revolution, developed the technique in the 1930s. He was an industrialist, inventor and founder of Toyota Industries. His method became popular in the 1970s, and Toyota still uses it to solve problems today.

Toyota has a "go and see" philosophy. This means that its decision making is based on an in-depth understanding of what's actually happening on the shop floor, rather than on what someone in a boardroom thinks might be happening.

The 5 Whys technique is true to this tradition, and it is most effective when the answers come from people who have hands-on experience of the process being examined. It is remarkably simple: when a problem occurs, you drill down to its root cause by asking "why?" five times. Then, when a counter-measure becomes apparent, you follow it through to prevent the issue from recurring.


The 5 Whys uses "counter-measures," rather than solutions. A counter-measure is an action or set of actions that seeks to prevent the problem arising again, while a solution may just seek to deal with the symptom. As such, counter-measures are more robust, and will more likely prevent the problem from recurring.

When to Use the 5 Whys

You can use 5 Whys for troubleshooting, quality improvement and problem solving, but it is most effective when used to resolve simple or moderately difficult problems.

You need to be more careful when you're tackling complex or critical problems. 5 Whys can lead you to pursue a single track, or a small number of tracks, of enquiry when there could be multiple causes. In cases such as these, a wider-ranging method such as Cause and Effect Analysis or Failure Mode and Effects Analysis may be more effective.

This simple technique, however, can often direct you quickly to the root(s) of a problem. So, whenever a system or process isn't working properly, give it a try before you embark on a more in-depth approach – and certainly before you attempt to develop a solution.

This tool's simplicity gives it great flexibility, too, and it combines well with other methods and techniques, such as Root Cause Analysis. It is often associated with Lean Manufacturing, where it is used to identify and eliminate wasteful practices. It is also used in the analysis phase of the Six Sigma quality improvement methodology.

How to Use 5 Whys

The model follows a very simple seven-step process:

Step 1. Assemble a Team

Gather together people who are familiar with the detail of the problem and with the process that you're trying to fix. Include someone to act as a facilitator, who can keep the team focused on identifying effective counter-measures.

Step 2. Define the Problem

If you can, observe the problem in action. Discuss it with your team and write a brief, clear problem statement that you all agree on. For example, "Team A isn't meeting its response time targets" or "Software release B resulted in too many rollback failures."

Then, write your statement on a whiteboard, leaving enough space around it to write your answers to the repeated question, "Why?"

Step 3. Ask the First "Why?"

Ask your team why the problem is occurring. (For example, "Why isn't team A meeting its response time targets?")

Asking "why?" sounds simple, but answering it requires thought and intelligent application. Search for answers that are grounded in fact: they must be accounts of things that have actually happened – not guesses at what might have happened.

This prevents 5 Whys from becoming just a process of deductive reasoning, which can generate a large number of possible causes and, sometimes, create more confusion as you chase down hypothetical problems.

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Your team members may come up with one obvious reason why, or several plausible ones. Record their answers under (or to the right of) your problem statement as succinct phrases, rather than single words or lengthy statements. For example, saying "volume of calls is too high" is better than a vague "overloaded."

Step 4. Ask "Why?" Four More Times

Working sequentially along one of the answers you generated in Step 3, ask four further "whys" in succession. Frame the question each time in response to the answer you've just recorded, and again record your responses to the right.


Try to move on quickly from one question to the next, so that you have the full picture before you jump to any conclusions.

The diagram, below, shows an example of 5 Whys in action in a simple format, following a single lane of inquiry.

Figure 1: 5 Whys (single lane)

5 Whys

5 Whys also allows you to follow multiple lanes of inquiry, as we show in Figure 2, below.

In our example, asking "Why was the delivery late?" identifies a second answer (Reason 2). Asking "Why?" for that answer reveals a single reason (Reason 1), which you can address with a counter-measure.

Similarly, asking "Why did the job take longer than expected?" has a second answer (Reason 2), and asking "Why?" at this point reveals a single reason (Reason 1). Another "Why?" here identifies two possibilities (Reasons 1 and 2) before a possible counter-measure.

There is also a second reason for "Why we ran out of printer ink" (Reason 2), and a single answer for the next "Why?" (Reason 1), that can then be addressed with a counter-measure.

Figure 2: 5 Whys (multiple lanes)

5 Whys

Step 5. Know When to Stop

You'll have revealed the nature of the root cause when asking "why" produces no more useful responses and you can go no further. An appropriate counter-measure or process change should then become evident. (As we said earlier, if you're not sure whether you've uncovered the real root cause, consider using a more in-depth problem-solving technique like Cause and Effect Analysis, Root Cause Analysis or FMEA.)

Tip 1:

The "5" in 5 Whys is really just a "rule of thumb." In some instances, you may need to go on and ask "why?" a few more times before you get to the root of the problem. In others, you may reach this point before you ask your fifth "why?" If you do, be careful that you've not stopped too soon, and that you're not simply accepting "knee-jerk" responses.

The important point is to stop asking "why?" when the useful responses stop coming.

Tip 2:

As you work through your chain of questioning, you'll often find that someone has failed to take a necessary action. The great thing about 5 Whys is that it prompts you to go further than just assigning blame, and to ask why that happened. This often points to organizational issues or areas where processes need to be improved.

If you identified more than one reason in Step 3, repeat this process for the different branches of your analysis until you reach a root cause for each one.

Step 6. Address the Root Cause(s)

Now that you've identified at least one true root cause, you need to discuss and agree what counter-measures will prevent the problem from recurring.

Step 7. Monitor Your Measures

Keep a close watch on how effectively your counter-measures eliminate or minimize the initial problem. You may need to amend them, or replace them with something different. If this happens, it would be sensible to repeat the 5 Whys process to ensure that you've identified the correct root cause.


Key Points

The 5 Whys strategy is a simple, effective tool for uncovering the root of a problem. You can use it in troubleshooting, problem solving and quality improvement initiatives.

Start with a problem and ask "why" it is occurring. Make sure that your answer is grounded in fact, then ask "why" again. Continue the process until you reach the problem's root cause, and you can identify a counter-measure that prevents it from recurring.

Bear in mind that this questioning process is best suited to simple to moderately-difficult problems. Complex problems may benefit from a more detailed approach (although using 5 Whys will still give you useful insights).

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Comments (54)
  • Over a month ago Yolande wrote
    Hi Harrison2007

    We're glad you enjoyed the article. When you start using the 5Why technique, you'll see that it's a powerful tool!

    Mind Tools Team
  • Over a month ago Harrison2007 wrote
    I liked this tool, it makes it easy and simple for problems that we cannot figure out what the root cause. This simple "Why" helps focus on the real problem and no assume or guess what is happening.
  • Over a month ago BillT wrote
    Hi bk1991,

    It's good to hear that you were able to put the tool to practical use. Hopefully you were able to identify the root cause and address the problem with an appropriate solution. Thanks for the feedback.
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