Enter Failure Modes
Example Data Table
Sample failure modes and scores, with RPN computed as S × O × D.
| Failure Mode | Effect | Cause | S | O | D | RPN |
|---|---|---|---|---|---|---|
| Label mismatch on packaging | Wrong product shipped to customer | Similar SKUs, manual picking error | 7 | 5 | 6 | 210 |
| Weld porosity in joint | Reduced strength, potential field failure | Contaminated surface, wrong parameters | 8 | 4 | 5 | 160 |
| Torque drift on fasteners | Loose assembly, rework and downtime | Uncalibrated tool, operator variation | 6 | 4 | 4 | 96 |
Formula Used
This tool follows a common Failure Mode and Effects Analysis approach using the Risk Priority Number (RPN).
- Severity (S): impact level if the failure occurs (1–10).
- Occurrence (O): likelihood of the cause happening (1–10).
- Detection (D): ability to detect before release (1–10; higher = harder).
- RPN: RPN = S × O × D
- Weighted RPN (optional): (S×wS) × (O×wO) × (D×wD)
How to Use This Calculator
- Click Add Row and describe each failure mode.
- Enter the effect, cause, and current controls for context.
- Score Severity, Occurrence, and Detection from 1 to 10.
- Adjust thresholds if your organization uses different cutoffs.
- Press Analyze Failure Modes to rank risks.
- Download CSV or PDF to share in audits and reviews.
Scoring
Using the Risk Priority Number, the calculator multiplies Severity, Occurrence, and Detection scored from 1 to 10. That creates an RPN range from 1 to 1000, making rank-ordering straightforward. Consistency matters: define score anchors, review recent defects, and calibrate teams quarterly. When two modes tie, compare Severity first, then Detection. Recording effects, causes, and controls beside the scores improves traceability for reviews and corrective-action records. Keep rating tables shared and versioned.
Thresholds
Action thresholds convert scores into decisions. Many quality groups treat RPN ≥ 200 as urgent, 100–199 as planned, and <100 as monitor, but you can align cutoffs to customer impact. A Severity threshold is often stricter: any mode with S ≥ 8 should trigger action even if the RPN is modest. This calculator lets you set your own limits so the risk labels match your governance rules. Document exceptions for special processes.
Weighting
Weighted scoring helps when some dimensions matter more. For safety-critical products you may weight Severity higher, for example wS=1.3, while keeping wO=1.0 and wD=1.0. The tool’s weighted RPN multiplies the adjusted components, emphasizing the factors you care about without changing the familiar 1–10 inputs. Use weights sparingly, document the rationale, and keep them stable across projects to preserve comparability. Review weights with engineering monthly.
Detection
Detection is the most actionable lever because it reflects control strength. Improving Detection means moving from end-of-line discovery to in-process prevention: poka‑yoke fixtures, automated vision checks, torque monitoring, and SPC alarms. If Detection drops from 7 to 3 while S and O remain 6 and 4, the RPN falls from 168 to 72, a 57% reduction. Capture the control type and measurement method so improvements are auditable. Validate detection scores using samples.
Reporting
Reports keep FMEA work alive after the workshop. Exporting CSV supports trend tracking across lines, suppliers, or product revisions, while the PDF snapshot is useful for audits. Re-run the analyzer after corrective actions to show before/after RPN reductions and to update priority rankings. Pair top modes with owners, due dates, and verification steps, then review monthly. Continuous improvement is demonstrated when the ranked list changes for good reasons. Archive revisions for future recalls.
FAQs
What does the calculator output for each failure mode?
It calculates RPN (Severity × Occurrence × Detection), assigns a risk label using your thresholds, and ranks modes from highest to lowest so you can prioritize actions.
When should I use Weighted RPN instead of standard RPN?
Use weights when one dimension must dominate decisions, such as safety or regulatory impact. Keep weights documented and stable so comparisons remain meaningful across teams and time.
Should we act on a high Severity score even if RPN is low?
Yes. Many programs treat Severity as a gate: if S is at or above your critical limit, plan mitigation even when Occurrence is rare or Detection is strong.
How do I select realistic Detection scores?
Base Detection on current controls and evidence. Strong in‑process prevention and automated checks score lower numbers, while reliance on final inspection or subjective judgment scores higher. Calibrate using recent escape or audit data.
Can I share results with auditors or suppliers?
Yes. Export CSV for analysis and trend reporting, and export PDF for a fixed snapshot. Include the same scoring definitions and thresholds so external reviewers interpret risk consistently.
How often should we re-run the analysis?
Re-run after any corrective action, process change, supplier change, or new complaint trend. A monthly review for top risks works well, and a full refresh each release keeps the list current.