Quality Risk Management — ICH Q9
FMEA Risk Priority Number (RPN) Calculator
Log failure modes with Severity, Occurrence, and Detection ratings to calculate and rank RPN — a core risk-ranking tool used in process design (Stage 1) and quality risk management.
How RPN Works
Failure Mode and Effects Analysis (FMEA) scores each potential failure mode on three factors, each typically rated 1–10, then multiplies them to produce a Risk Priority Number (RPN) used to prioritize mitigation efforts.
| Factor | 1 (Low) | 10 (High) |
|---|---|---|
| Severity | Negligible effect on product/patient | Critical/hazardous, no warning |
| Occurrence | Extremely unlikely to occur | Almost certain to occur |
| Detection | Almost certain to be detected before impact | Cannot be detected before impact |
Note that a high Detection score means low detectability (harder to catch) — this is the most commonly misapplied factor in practice.
Interactive FMEA Worksheet
| Process Step | Potential Failure Mode | S | O | D | RPN |
|---|
Using RPN to Prioritize Action
| RPN Range | Typical Priority |
|---|---|
| 1 – 49 (Low) | Monitor; no immediate action typically required |
| 50 – 99 (Medium) | Consider risk-reduction actions, especially if Severity is high |
| 100+ (High) | Prioritize mitigation — tighter control, added detection, or design change |
RPN thresholds are illustrative, not universal — many organizations define their own risk acceptance thresholds and matrices in their Quality Risk Management procedure. A high Severity score alone (regardless of RPN total) often warrants attention even if occurrence/detection scores are favorable — some QRM programs apply a Severity-based override rule for this reason.
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