A3 Problem Solving: How to Write an A3 Report Step by Step

By Mirko Peters · 2026-11-11

A3 problem solving on one page: how to write an A3 report step by step, a template layout, a worked example with numbers and how to coach others to use it well.

A3 problem solving is a structured way to solve a problem and tell the story of the solution on a single sheet of paper. An A3 report names the problem, shows the current condition with data, sets a goal, finds the root cause, proposes countermeasures and plans the follow-up. This article is for lean managers who need to write A3 reports correctly and teach others to do the same. It walks through each step, gives a template layout and a worked example, and ends with coaching questions and common mistakes.

Key points

• An A3 report tells a problem-solving story on one sheet: the left side covers the problem and current condition, the right side covers countermeasures and follow-up.
• The value of an A3 lies in the thinking and the dialogue it forces, not in the paper, so write it with data from the gemba.
• Root cause analysis comes before countermeasures: use the 5 whys on facts, or a fishbone diagram first when several causes interact.
• An A3 records a PDCA cycle, so it must include a plan for checking the result and for standardizing what works.
• Coach by asking questions such as how the root cause was confirmed and how each countermeasure addresses a cause.

What is A3 problem solving?

The Lean Enterprise Institute (LEI) describes the A3 report as a Toyota-pioneered practice. The name comes from the paper: A3 is the international term for a sheet 297 millimeters wide and 420 millimeters long, close to the US 11 by 17 inch tabloid sheet. Read more in the LEI article on the many facets of the A3.

Teams use A3s inside continuous improvement work, for example to document a kaizen project. The same article separates two ideas. A3 thinking is a systematic approach to resolving problems or improving work processes, and it can be followed whether or not the findings are written on an A3 sheet. The A3 report is the storyboard that helps with communication, collaboration and coordination, and that helps the owner gain buy-in for changes.

IndustryWeek's primer on A3 reports, based on a talk by Durward Sobek of Montana State University, adds a useful point: the report is a communication tool for dialogue between people, and the process of creating it is the real value. It also says A3 reports record the main results of the PDCA cycle. Sobek's words: following the structure means "you are actually doing PDCA even if you don't call it that". The PDCA cycle is the plan, do, check, act loop behind the page.

How do you write an A3 report step by step?

LEI describes the layout in simple terms: the left side covers the problem or current condition, and the right side covers the countermeasures that were considered, tested and chosen. A common order of sections is below. Adapt the names to your company.

1. Header. Title, owner (the byline), date and the person who will read it and approve it (the "to" line). Write for that reader.
2. Background. Why does this problem matter? Link it to safety, quality, delivery or cost, and to a business goal. Keep it to a few lines.
3. Current condition. Describe the process as it is, with data from the gemba (the Japanese word for "the real place", the shop floor). Use a simple diagram or a chart. State the problem in one precise sentence with a number.
4. Goal. A measurable target and a date. For example, "reduce leak-test rejects from 4.8% to 2.4% by the end of the quarter".
5. Root cause analysis. Find the cause, not the symptom. Use the 5 whys on observed facts. For a complex problem with several interacting causes, start with a fishbone diagram. More on this below.
6. Countermeasures. List what you will do to remove each cause, who is responsible and by when. Choose the countermeasures with the best effect for the effort.
7. Implementation plan. A short timeline with owners, including a trial on a small scale.
8. Follow-up. How and when you will check the result, how you will standardize what works and what you will do if the target is missed.

Treat the A3 as a working document. It is updated as you learn, and the owner talks it through with the reader at the gemba.

How do you find the root cause?

Root cause analysis is the heart of the A3. Two tools help most.

The ASQ glossary describes the Five Whys as a root cause analysis technique that involves repeatedly asking why. It is typically run about five times, though more or fewer is fine, and it credits Sakichi Toyoda with developing it. The rules: start with a precise problem statement backed by data, answer each why with an observed fact and not a hypothesis, stop at a cause you can act on, and verify the root cause before you act.

The Five Whys works best for linear chains of cause and effect. For complex problems with several interacting causes, use a fishbone (Ishikawa) diagram, which lays out hypotheses on one picture, and then apply the 5 whys to the most likely branches. The iSixSigma article on Ishikawa diagrams and the 5 whys recommends exactly this combination, and it warns that stopping at the first plausible cause leads to actions that only treat symptoms.

A3 template: what goes where

Draw the sheet in two columns. Use boxes with aligned edges.

• Top: title, owner, date, "to" line.
• Left column: background, current condition (with chart), goal, root cause analysis (with the 5 whys or fishbone).
• Right column: countermeasures, implementation plan, follow-up and results.

Add a small box at the bottom for open issues. Keep text short, with bullets and pictures. If it does not fit on one sheet, the problem statement is probably too broad.

Example: leak-test rejects

This example uses assumed numbers.

A line produces 5,000 housings per month and 240 fail the leak test, a reject rate of 4.8%. The team's goal is 2.4%, or 120 rejects.

A check of the 240 rejects shows 130 (54%) with a misplaced seal, 60 (25%) with porosity and 50 (21%) from other causes.

Five whys for the misplaced seal. Why was the seal misplaced? The operator places it by hand without a guide. Why no guide? The fixture has no stop for the seal. Why? The fixture was built before the latest variant. Why was it not updated? New variants do not trigger a fixture check.

Countermeasures. Add a stop to the fixture, and add a fixture check to the checklist for new variants. The team expects to remove about 80% of the seal rejects.

Check the arithmetic. 80% of 130 is 104. Rejects fall from 240 to 136, a rate of 136 ÷ 5,000 = 2.7%. That is better, but it does not reach the goal of 2.4%. The follow-up section therefore needs a second countermeasure aimed at porosity. The A3 shows this gap early, which is exactly its purpose.

How do you coach an A3?

Lean managers teach A3 by asking questions, not by writing the report for the author. Useful questions:

• How did you confirm this is the root cause, and not just a symptom?
• How does this countermeasure address that cause?
• What data supports the current condition? Did you see it at the gemba?
• What will you check, and when?
• What did you learn from the trial?

Review the A3 in short, regular sessions at the owner's workplace. Ask the author to explain it in a few minutes. If the story is not clear, the thinking is not clear.

Common mistakes

• Writing the A3 at the end. It then becomes a report and not a thinking tool.
• Jumping to countermeasures. A solution before a cause is a guess.
• Stopping at the first answer. A plausible cause is not a verified cause.
• Vague goals. "Improve quality" cannot be checked. Use a number and a date.
• Too much text. If nobody reads it in two minutes, shorten it.
• No follow-up. Without a check, there is no learning and no standard.

How software can help

A3s are often drawn by hand, and many teams prefer that. Software helps when you must keep many of them: it can store each A3 with its owner and status, link countermeasures to actions with due dates, and make them visible across sites. Look for a view that mirrors the paper layout and for easy photos of the real situation. Keep the conversation at the gemba, and use the tool only as the record.

Next step

Pick one real problem in your area, draw the two-column sheet and write the problem statement with a number. Take the draft to the gemba and review it with the people who do the work. That is how A3 problem solving starts to work in your plant.