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Pareto Chart Generator
Paste defect, downtime or complaint categories with their counts. Get them sorted largest first, each category's share, the cumulative percentage line, and the vital few that make up most of the total.
Pareto chart generator
| Category | Count | Share | Cumulative |
|---|---|---|---|
| Porosity | 48 | 48 % | 48 % |
| Dimensional out of tolerance | 30 | 30 % | 78 % |
| Scratch | 12 | 12 % | 90 % |
| Burr | 6 | 6 % | 96 % |
| Wrong label | 4 | 4 % | 100 % |
| Step | Formula | Value |
|---|---|---|
| Total | Σ counts = 48 + 30 + 12 + 6 + 4 | 100 |
| Share and cumulative share | Porosity: 48 / 100 → cumulative | 48 % → 48 % |
| Share and cumulative share | Dimensional out of tolerance: 30 / 100 → cumulative | 30 % → 78 % |
| Share and cumulative share | Scratch: 12 / 100 → cumulative | 12 % → 90 % |
| Share and cumulative share | Burr: 6 / 100 → cumulative | 6 % → 96 % |
| Share and cumulative share | Wrong label: 4 / 100 → cumulative | 4 % → 100 % |
| Vital few | Categories up to 80 % cumulative | 3 of 5 (90 %) |
Formulas used
- Total
- N = Σ countᵢ
- Share of each category
- shareᵢ = countᵢ / N
- Cumulative share (sorted descending)
- cumᵢ = (count₁ + … + countᵢ) / N
- Vital few
- categories up to and including the first one where cumᵢ ≥ threshold
Assumptions and limits
- Categories are mutually exclusive: each defect or event is counted in exactly one category.
- All counts cover the same period, product and measurement method.
- Counts can be occurrences, cost, or minutes of downtime, but use one measure for every category.
- The threshold (80% by default) is a convention for drawing the line, not a law. Real data rarely splits exactly 80/20.
- Ties keep the order you entered them in.
Worked example
Illustrative example: a month of rejects at final inspection, recorded as porosity 48, dimensional out of tolerance 30, scratch 12, burr 6 and wrong label 4.
| Step | Formula | Value |
|---|---|---|
| Total | Σ counts = 48 + 30 + 12 + 6 + 4 | 100 |
| Share and cumulative share | Porosity: 48 / 100 → cumulative | 48 % → 48 % |
| Share and cumulative share | Dimensional out of tolerance: 30 / 100 → cumulative | 30 % → 78 % |
| Share and cumulative share | Scratch: 12 / 100 → cumulative | 12 % → 90 % |
| Share and cumulative share | Burr: 6 / 100 → cumulative | 6 % → 96 % |
| Share and cumulative share | Wrong label: 4 / 100 → cumulative | 4 % → 100 % |
| Vital few | Categories up to 80 % cumulative | 3 of 5 (90 %) |
Result: 3 categories make up 90% of the 100 rejects. Porosity and dimensional together reach 78%, so scratch is the category that crosses the 80% line.
How to build and read a Pareto chart
Pick one measure and one period
A Pareto chart ranks categories by a single measure. Counts of defects are the usual choice, but cost or downtime minutes often rank the same categories differently. A rare defect that scraps an expensive casting can matter more than a common cosmetic one. If you have both, build both charts and compare.
Use one period and one product or line. Mixing a month of line A with a week of line B ranks the data collection, not the problem.
Read the bars, then the line
The bars show each category's count, largest first. The line shows the running total as a percentage. Where the line flattens, extra categories add little. The vital few sit to the left of the point where the line crosses your threshold.
A chart with no clear break, where the bars fall off slowly and the line rises almost straight, is a finding too. It usually means the categories are too broad or too fine. Regroup them and look again.
Use it to choose, then to confirm
Pareto analysis is one of Ishikawa's seven basic quality tools. Its job is to choose where to dig. Take the top category into root-cause work, for example the D4 step of an 8D, and keep the data. After the fix, rebuild the chart for the same period length. The bar you worked on should shrink and the ranking may change.
Watch the 'Other' bar
Lumping small categories into 'Other' keeps the chart readable. If 'Other' grows into one of the biggest bars, it is hiding something. Split it.
Common mistakes
- Counting one defect in two categories. Overlapping categories inflate the total and distort every share.
- Ranking by count when cost is what matters. Run a second chart by cost of poor quality before committing resources.
- Treating 80/20 as a rule. Use the threshold to draw the line, not to expect a particular split.
- Comparing before and after charts of different lengths. Normalize to the same period or production volume first.
- Letting 'Other' dominate. A large 'Other' bar means the category list needs work.
Frequently asked questions
How do I make a Pareto chart?
List each category with its count, sort from largest to smallest, and divide each count by the total to get its share. Add the shares cumulatively and plot the bars with the cumulative percentage line on a second axis. This generator does all of that when you paste category, count pairs.
What is the 80/20 rule in a Pareto chart?
It is the observation, popularized by Joseph Juran, that a few causes often account for most of the effect. The 80% line is a convenient threshold for separating the vital few. Your data may split 70/30 or 90/10.
What format should I paste?
One category per line, with the count after a tab, comma or semicolon. A paste of two columns from a spreadsheet works directly. With tab-separated data, a comma inside the count is read as a thousands separator.
Should I use counts or cost?
Use whichever matches the decision. Counts show what happens most often. Cost shows what hurts most. The cost of poor quality calculator helps put a cost on each category.
How many categories should a Pareto chart have?
Enough to separate causes you would act on differently, usually somewhere between 5 and 10 plus an 'Other' bar. This tool accepts up to 50.
Sources
- Juran, J. M., Juran's Quality Handbook, McGraw-Hill: the Pareto principle and the vital few.
- Ishikawa, K., Guide to Quality Control, Asian Productivity Organization: the Pareto diagram as one of the seven basic tools.
- ASQ, Quality Tools: Pareto chart.
Results are computed in your browser from the published formulas named above. They are an engineering aid, not a substitute for the governing standard, your drawing, or your customer's requirements.