The 5 Whys: Simple Root Cause Analysis

4 min read · Updated July 2026

The 5 Whys is the simplest root-cause tool there is: you ask "why?" repeatedly until you reach the underlying cause rather than a symptom. Done well, it stops teams from fixing the wrong thing.

How it works

Start with the problem and ask why it happened. Take the answer and ask why again. Repeat — usually about five times — until you reach a cause that, if fixed, would stop the problem recurring. "Five" is a guide, not a rule.

A worked example

1. The delivery was late. Why? The order was picked late.
2. Why? The picker could not find the item. Why? It was in the wrong location.
3. Why? It was put away in a hurry. Why? There is no standard put-away process.
4. Root cause: no standard work for put-away — so the fix is to create one, not to blame the picker.

Common pitfalls

• Stopping at a symptom or a person rather than a process cause.
• Following a single chain when there are several contributing causes.
• Guessing instead of verifying each answer with evidence.

When to use a fishbone instead

If a problem has many possible causes across different categories (people, process, equipment, materials), a fishbone (Ishikawa) diagram maps them all first — then you use the 5 Whys to drill into the most likely branches.