Try these sample inputs to see how rankings behave.
| Category | Source | Defects | S | O | D | Cost/Defect | Downtime (min) |
|---|---|---|---|---|---|---|---|
| People | Shift handoff errors | 12 | 6 | 5 | 6 | 8.00 | 15.0 |
| Machine | Filler nozzle wear | 18 | 7 | 6 | 5 | 12.00 | 35.0 |
| Method | Incorrect torque sequence | 9 | 8 | 4 | 7 | 15.00 | 10.0 |
| Material | Supplier lot variation | 22 | 5 | 7 | 6 | 6.00 | 0.0 |
| Environment | Humidity drift | 6 | 4 | 3 | 6 | 3.00 | 0.0 |
- Total Defects = Σ defects.
- Pareto % = (defects ÷ total) × 100, sorted by defects.
- Cumulative % = running sum of Pareto %.
- RPN = Severity × Occurrence × Detection.
- Impact = defects × severity.
- Cost Impact = defects × cost per defect.
- Time Impact = downtime minutes × (downtime cost per hour ÷ 60).
- Priority Score = Impact + (RPN×RiskWeight) + (CostImpact×CostWeight) + (TimeImpact×TimeWeight).
Adjust weights if your site values risk, cost, or downtime differently.
- List suspected sources using the Category and Source fields.
- Enter defects and the 1–10 ratings for Severity, Occurrence, and Detection.
- Add optional cost per defect and downtime minutes for financial impact.
- Set weights and Pareto threshold to match your quality priorities.
- Press Find Problem Sources and start with Priority Rank #1.
- Download CSV or PDF to share corrective action plans.
Why Source Ranking Matters
Quality issues rarely come from one place, so ranking turns opinions into action. This calculator scores each suspected source using defects, severity, risk, cost, and downtime. For example, 18 defects at severity 7 creates an impact of 126, before any weights. When the top two sources contribute over 50% of defects, fixing them first typically shortens investigation cycles and reduces rework hours on the next shift. Consistent rating rules keep comparisons fair.
How Pareto Targets Defect Volume
Pareto analysis sorts sources by defect counts and calculates each share of total defects. If total defects equal 67 and a material issue has 22 defects, its Pareto percent is 32.84%. The cumulative percent then shows how many sources explain most failures. With an 80% threshold, you may focus on three or four sources, while documenting the remainder as lower-priority opportunities for later kaizen. Review Pareto monthly to detect drift and seasonality.
Risk Priority Numbers for Hidden Failure
RPN strengthens the view when defect volume is low but risk is high. It multiplies Severity, Occurrence, and Detection on a 1–10 scale. A method error rated S=8, O=4, D=7 yields RPN=224, signaling a hard-to-detect issue. Using the Risk Weight converts RPN into a comparable contribution to Priority Score, preventing rare but critical hazards from being ignored. Track RPN changes after controls. Detection improved from 7 to 3 cuts RPN 57% quickly.
Cost and Downtime Convert Quality to Money
Operational data turns quality losses into currency. Cost Impact equals defects multiplied by cost per defect, such as 12 defects × 8 = 96. Time Impact converts downtime minutes using the downtime cost per hour, so 35 minutes at 120 per hour becomes 70. These values let leaders compare prevention versus correction and justify maintenance, training, or supplier containment with a clear return-on-effort narrative. Include warranty claims per unit shipped when relevant.
Using Weights for Site-Specific Decisions
Weights let you match scoring to business priorities. If safety is dominant, increase Risk Weight; if scrap is the pain point, increase Cost Weight; if throughput is fragile, increase Time Weight. Keeping weights near 0.10–2.00 avoids drowning impact. After recalculating, compare Priority Rank with Pareto Rank: a source that is top-five in both usually delivers the quickest measurable improvement. Lock weights per line for consistency. Revisit weights after audits or new tooling.
What does the Priority Score represent?
It is a weighted sum of impact, RPN contribution, cost impact, and downtime impact. Higher scores indicate sources that combine frequent defects with high consequence and measurable loss.
When should I change the weights?
Change weights when business goals shift, such as safety campaigns, scrap reduction targets, or capacity constraints. Keep weights stable during a study window so rankings remain comparable across weeks.
Why can a low-defect source rank high?
High severity, frequent occurrence, poor detection, or expensive downtime can push a source up. This flags issues that are rare but dangerous or costly.
How do I pick Severity, Occurrence, and Detection?
Use your site’s FMEA guidelines. Severity reflects consequence, Occurrence reflects likelihood, and Detection reflects control strength. Keep rating anchors written so different teams score the same scenario consistently.
What does the Pareto threshold do?
It sets the cumulative defect percentage used to define the focus bucket. At 80%, the bucket includes sources responsible for roughly four-fifths of defects.
Can I export and share results?
Yes. After calculating, use the CSV for analysis in spreadsheets and the PDF for quick reviews. Re-run the calculator before exporting to ensure the report reflects the latest inputs.