FMEA RPN Calculator
Calculate Risk Priority Number (RPN) and Action Priority (AP) from Severity, Occurrence & Detection ratings
1 = No effect → 10 = Hazardous
1 = Eliminated → 10 = Every time
1 = Certain detect → 10 = No detection
RPN
125
max 1,000
Action Priority
L
Low
Low — Continue monitoring
FMEA and RPN: The Complete Guide to FMEA Risk Priority Number
What is the FMEA Risk Priority Number (RPN)?
The Risk Priority Number (RPN) is a numerical metric used in Failure Mode and Effects Analysis (FMEA) to evaluate the relative risk of potential failure modes. It helps quality engineers prioritize corrective actions and mitigation strategies.
Each of the three parameters is rated on a scale from 1 to 10, meaning the total RPN score ranges from 1 to 1,000.
Severity (S)
Measures the severity of the effect of the failure mode on the end-user, assembly worker, or product. (1 = No effect, 10 = High safety/regulatory risk).
Occurrence (O)
Rates the likelihood or frequency of the failure cause occurring during the planned operating life. (1 = Extremely unlikely, 10 = Inevitable).
Detection (D)
Evaluates the effectiveness of current design or process controls in detecting the failure before reaching the customer. (1 = Almost certain, 10 = Undetectable).
The Pitfalls of Traditional RPN FMEA
Relying purely on a threshold RPN (e.g., "all failure modes with RPN > 100 require action") is a common industry mistake. RPN fails to distinguish between different risk profiles. Look at this comparison:
| Failure Mode | Severity (S) | Occurrence (O) | Detection (D) | RPN | Risk Level / Action Needs |
|---|---|---|---|---|---|
| Mode A: Steering Failure | 10 | 2 | 2 | 40 | Critical Safety Issue (Requires Action!) |
| Mode B: Loose Cup Holder | 4 | 5 | 2 | 40 | Minor Inconvenience (Low Priority) |
Both modes have the exact same RPN of 40, but Mode A represents a critical steering safety issue (S=10), whereas Mode B is a minor cosmetic issue (S=4). Under a simple RPN threshold rule, both would be treated identically.
The AIAG & VDA Harmonized Standard: Action Priority (AP)
To address the mathematical limitations of RPN, the harmonized AIAG & VDA FMEA Handbook (2019) introduced the **Action Priority (AP)** logic tables. AP categorizes risks into:
- High (H): Immediate corrective actions must be taken to reduce risk (Severity and Occurrence must be lowered).
- Medium (M): Action is recommended. The team should evaluate current controls and attempt to reduce risk.
- Low (L): Current prevention and detection controls are sufficient. No further action is required.
Our calculator above automatically determines both the RPN and the official AIAG & VDA Action Priority, giving you a complete overview for your quality audits and PPAP/PPA submittals.