Calculate Risk Priority Number and Action Priority for any failure mode. Choose between AIAG/VDA (1–10) and ICH Q9 (1–5) scoring scales. No sign-up required.
Risk Priority Number
5 × 5 × 5 = 125
Action Priority
LowBased on the specific S‑O‑D combination per AIAG‑VDA 2019 — not the RPN product.
| Risk Level | RPN Range |
|---|---|
| Low | 1–49 |
| Medium | –124 |
| High | –1000 |
Severity × Occurrence per ISO 14971.
This calculates one failure mode. Mitigon manages your entire FMEA.
Build your full FMEA for freeRPN (Risk Priority Number) is how FMEA teams measure and rank risk. You score three factors independently, then multiply them:
The formula is simply RPN = S × O × D.
RPN has been central to FMEA since the automotive industry adopted it (AIAG), and it's now standard in pharma and medtech too. It's referenced in ICH Q9 (Quality Risk Management) and widely used in process validation, cleaning validation, equipment qualification, and supplier risk assessments. The classic AIAG/VDA scale scores each factor from 1 to 10, giving RPN values from 1 to 1,000. ICH Q9 implementations often use a simplified 5-level scale.
RPN is everywhere, but it has real limitations. Because it just multiplies three scores, it can mask risk: a failure mode with S=10, O=1, D=8 (RPN=80) and one with S=2, O=5, D=8 (RPN=80) have the same RPN but vastly different safety implications. The first could kill a patient but almost never happens; the second is a minor quality issue that comes up more often. RPN treats all three factors as equal, which doesn't match how regulators or clinicians think about risk. Severity almost always matters more than occurrence or detection.
The AIAG-VDA FMEA Handbook (2019) introduced Action Priority (AP) to replace RPN-based ranking. AP uses a lookup table that considers the specific combination of S, O, and D values (rather than their product) to assign a priority level (High, Medium, or Low). Many teams now report both RPN and AP while they transition. For new FMEAs, the trend in both automotive and life sciences is toward AP or similar approaches that look at the full S-O-D combination. Mitigon supports both RPN and Action Priority with configurable scoring scales.
Reference tables for both the classic AIAG/VDA 1–10 scale and the ICH Q9 5-level scale used in pharmaceutical risk management.
| Score | Severity | Occurrence | Detection |
|---|---|---|---|
| 1 | No discernible effect on product quality or patient safety | Failure is eliminated through preventive controls; ≤1 in 1,500,000 | Current controls always detect the cause; validated automated 100% in-process test |
| 2 | Minor cosmetic non-conformance; no impact on device function or patient | Rare isolated failures; ~1 in 150,000 | Very high detection probability; automated inspection with proven reliability |
| 3 | Minor non-conformance noticed by trained inspector; no patient impact | Very few failures; ~1 in 15,000 | High detection probability; multiple layers of inspection |
| 4 | Slight process deviation; product reworkable with no patient risk | Few failures; ~1 in 2,000 | Moderately high detection; statistical process controls in place |
| 5 | Process deviation requiring investigation; product may need rework | Occasional failures; ~1 in 400 | Moderate detection probability; routine inspection may catch the failure |
| 6 | Product partially non-conforming; batch disposition affected | Moderate failures; ~1 in 80 | Low detection probability; visual inspection with limited reliability |
| 7 | Product renders batch unusable or causes major non-conformance | Frequent failures; ~1 in 20 | Very low detection probability; inspection is difficult or subjective |
| 8 | Product non-functional or non-conforming; regulatory reportable event possible | High failure rate; ~1 in 8 | Remote chance of detection; control relies on operator judgment only |
| 9 | Potential patient harm with prior warning or detection opportunity | Very high failure rate; ~1 in 3 | Very remote chance of detection; no reliable control method available |
| 10 | Patient death or permanent injury without prior warning | Failure is almost certain; ≥1 in 2 | No detection method; control cannot detect the cause or failure mode |
| Score | Severity | Occurrence | Detection |
|---|---|---|---|
| 1 | No impact on product quality, patient safety, or data integrity | Extremely unlikely to occur; only under exceptional circumstances | Almost certain to detect; robust, validated detection methods |
| 2 | Minor impact on quality attributes; no effect on patient safety | Low probability of occurrence; strong preventive controls in place | High probability of detection; reliable monitoring in place |
| 3 | Significant impact on quality; potential for batch rejection | May occur periodically; preventive controls partially effective | Moderate detection capability; may miss intermittent failures |
| 4 | Serious impact on product quality; potential patient harm | Expected to occur regularly; weak or absent preventive controls | Low detection capability; limited monitoring available |
| 5 | Direct threat to patient safety; life-threatening consequences | Occurs repeatedly; no effective preventive controls | No detection capability; failure would go unnoticed |
These scales come built into Mitigon. Custom scoring, audit trails, and team collaboration included.
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