FMEA RPN calculator
Enter each failure mode with its severity (S), occurrence (O) and detection (D) ratings from 1 to 10. The tool calculates the risk priority number (RPN = S × O × D), ranks the rows, flags severity 9 and 10, and shows the RPN after your actions if you add revised ratings. A fictional example is loaded.
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| Failure mode | S | O | D | RPN | Revised |
|---|---|---|---|---|---|
| Seal missing after assembly | 8 | 5 | 4 | 160 | 48 (−70 %) |
| Wrong torque on M6 screw | 7 | 3 | 6 | 126 | – |
| Burr on edge | 4 | 6 | 5 | 120 | – |
| Crack in housing from drop at line ⚠ S≥9 | 9 | 2 | 5 | 90 | – |
| Label swapped between variants | 5 | 4 | 3 | 60 | – |
1 row(s) have severity 9 or 10. Review these regardless of RPN: a low RPN can hide a safety or regulatory effect.
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How it calculates
- RPN = S × O × D, so it ranges from 1 to 1000. Example: S 8, O 5, D 4 gives 160.
- Rows are sorted by RPN, then by severity, then by occurrence, so a higher severity comes first when RPNs are equal.
- Severity 9 or 10 is flagged on every row, whatever the RPN.
- Revised ratings: an empty field keeps the original value. Reduction = (RPN before − RPN after) ÷ RPN before. Example: O 5 → 2 and D 4 → 3 gives 160 → 48, a 70 % reduction.
- If you set a threshold, rows at or above it are marked. The tool has no built-in threshold.
Limits and assumptions
Assumption: you use 1–10 rating scales defined by your own procedure or your customer; the tool does not check what the numbers mean. RPN multiplies ordinal ratings, so equal RPNs can hide very different risks (the tool warns when that happens), and a fixed RPN threshold is not a reliable rule on its own. This tool uses RPN only. It does not apply the AIAG-VDA FMEA (2019) Action Priority (AP) table, which many automotive customers now ask for. Up to 50 rows, failure mode up to 120 characters. Not included: functions, effects, causes, controls and responsibilities; keep those in your FMEA form. Advisory only: verify against your own procedures and your customer's requirements.
New to FMEA? Read FMEA basics for 8D. After an 8D, update the PFMEA and control plan: see PFMEA and control plan update after an 8D.
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