FMEA Risk Priority Number Calculator

All three ratings follow the same direction on purpose: a higher number always means more risk. For Detection specifically, a high score doesn't mean your detection process is strong — it means the failure is unlikely to be caught before it reaches the customer, which is the worst-case outcome. A Detection score of 1 means you're almost certain to catch it; a 10 means it will slip through virtually undetected.

Criticality is Severity × Occurrence, calculated without factoring in Detection. It exists because some FMEA variants rank failure modes on how severe and how likely they are before considering whether current controls would catch them. Comparing RPN and Criticality side by side can reveal a failure mode that looks moderate by RPN but is actually severe and frequent, just well-covered by an existing detection control.

Yes, and it's one of the scale's known weaknesses. Because RPN is a straight product of three 1-10 ratings, a failure with Severity 5, Occurrence 4, and Detection 5 (RPN 100) scores identically to one with Severity 10, Occurrence 2, and Detection 5 (also RPN 100) — even though the second involves a hazardous, safety-critical failure. That's why this calculator separately flags any Severity of 9 or 10 as its own hazardous band regardless of the resulting RPN.

Use them to triage a list of failure modes against each other, not as a standalone verdict on any one failure. The built-in thresholds (200+ High Risk, 120-199 Medium-High, 80-119 Medium, 40-79 Low-Medium, below 40 Low) are a common industry convention, but many teams override them with a severity floor — for example, escalating any failure with Severity 9 or 10 to immediate action even if its RPN falls in a lower band.