What is a Risk Priority Number?

A Risk Priority Number (RPN) is a calculation of the overall risk when completing a Failure Mode and Effects Analysis (FMEA).

RPN Calculation

The RPN is a calculated score comprising of Severity (S), Occurrence (O) and Detection (D) from an FMEA process. Each of the S.O.D. scores is assigned to a potential failure mode identified during the initial analysis stage of the FMEA.

The final RPN value is then evaluated with respect to the ultimate risk of the individual failure modes. In general, the higher the RPN the greater the risk, however, this is not always the case.

Here is an example where one of the failure modes would require greater attention than the others despite having the same scores:

risk priority number example

With a high Severity and high Occurrence but a low detection score, failure mode 2 is clearly more critical than the other two failure modes.


Visit our FMEA page for more details on the FMEA process and severity, occurrence, and detection.

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