Quality Engineering & Risk Analytics Lab

FMEA Risk Priority Number (RPN) Lab

Calculate Failure Mode and Effects Analysis (FMEA), Severity, Occurrence, Detection, RPN, and AIAG-VDA Action Priority in a free interactive engineering lab.

FMEA Matrix Failure Breakdown FMEA Theory FAQ

Engineering FMEA Presets

Load industry standard failure modes.

Step 1: Define Failure Modes, Causes & Controls

Failure Mode and Effects Analysis (FMEA) Scoring

Max Single RPN
280 / 1000
Severe single failure mode
Action Priority (AP)
2 Critical Items
Requiring mandatory mitigation
Cumulative System RPN
832 → 145
Total system portfolio RPN
Risk Reduction (%)
-82.6%
Post-mitigation risk reduction

FMEA Risk Priority & Action Mitigation Matrix

Failure Mode & Root Cause Initial (S / O / D)
RPN		 Initial Action Priority (AP) Revised (S / O / D)
RPN		 Revised Action Priority (AP) Net Risk Reduction

Quality Engineering Principles

RPN vs. AIAG-VDA Action Priority

Failure Mode and Effects Analysis (FMEA) is a cornerstone of Lean Six Sigma and modern reliability engineering:

  • Severity (S, 1-10): Assesses the gravity of the failure effect on safety, compliance, or customer satisfaction. Severity cannot be reduced without product redesign.
  • Occurrence (O, 1-10): Measures the frequency or probability of the failure cause occurring. Reduced via preventive poka-yoke (mistake-proofing).
  • Detection (D, 1-10): Measures the likelihood that current inspection and testing controls will catch the defect before reaching the end customer (1 = guaranteed catch, 10 = undetectable).
  • Action Priority (AP): Modern AIAG-VDA standard prioritizes Severity over pure RPN multiplication to prevent severe safety hazards from being masked by low occurrence.

Measure DMAIC process sigma in the Six Sigma Lab.

FMEA Mathematical Equations

Risk Priority formulas

Risk Priority Number (RPN) = Severity (S) × Occurrence (O) × Detection (D)

RPN Range = [1, 1000]

Δ RPN = Initial RPN - Revised RPN

Δ RPN (%) = (Δ RPN ÷ Initial RPN) × 100%

Cumulative System Risk = ∑ RPN(i)

Model operational downtime in the Business Continuity Lab.

FAQ

Failure mode & effects analysis questions

What is Failure Mode and Effects Analysis (FMEA)?

FMEA is a structured, systematic engineering and operational methodology used to identify potential failure modes, evaluate their severity and causes, and prioritize preventive controls.

How is the Risk Priority Number (RPN) calculated?

RPN is the product of Severity (1-10), Occurrence (1-10), and Detection (1-10): RPN = S x O x D, yielding a score between 1 and 1000.

What is the AIAG-VDA Action Priority (AP) method?

Action Priority (AP) replaces pure RPN thresholding by giving hierarchical priority to Severity. If Severity is 9 or 10, the risk receives High priority even if Occurrence or Detection is low.

How do mitigation controls reduce RPN?

Prevention controls eliminate root causes to reduce Occurrence (O), while inspection, sensors, and verification controls improve early discovery to lower Detection (D).

What is the difference between DFMEA and PFMEA?

Design FMEA (DFMEA) evaluates product design vulnerabilities and material specs, whereas Process FMEA (PFMEA) analyzes manufacturing, assembly, software deployment, and operational workflows.

Can I export the FMEA risk assessment to CSV?

Yes. You can export complete initial and revised Severity, Occurrence, Detection, RPN, and Action Priority logs as a UTF-8 CSV spreadsheet with formula defense.

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