FMEA Severity Rating Guide
Severity 1–10 scale at a glance
The full AIAG-VDA Severity scale, from minor cosmetic defects through hazardous failures. Use this as the team reference during rating workshops.
Severity (S) — 1 to 10
Severity of effect on the customer or downstream process
Minor annoyance, cosmetic, no functional impact
Degraded performance, customer complaint, rework
Loss of primary function, regulatory or warranty exposure
Safety or compliance failure, with or without warning
What is Severity in FMEA?
Severity is the rating that measures how serious the consequence of a failure would be if the failure reached the customer, user, next manufacturing operation or regulatory authority.
Severity does not measure how often something happens. It does not measure how likely a control is to detect a defect. It only measures the impact of the failure effect.
Within the AIAG-VDA methodology, Severity is one of the three ratings used during Risk Analysis together with Occurrence and Detection. Because Severity reflects the consequence of failure, it often remains unchanged unless the design, process or resulting effect itself changes.
Why Severity Matters More Than Most Teams Think
Many organizations spend most of their workshop time debating Occurrence and Detection ratings while treating Severity as a quick estimate. This is a mistake.
Severity drives customer impact, safety concerns, warranty exposure, regulatory compliance and Action Priority decisions. An incorrect Severity rating can distort the entire FMEA.
High-Severity failure modes deserve deeper engineering discussion because they represent the greatest potential business and customer risk.
AIAG-VDA Severity Scale Overview
| Severity | General Meaning | Typical Impact |
|---|---|---|
| 10 | Hazardous | Safety or regulatory issue |
| 9 | Very High | Loss of primary function |
| 8 | High | Major customer dissatisfaction |
| 7 | Significant | Reduced product performance |
| 6 | Moderate | Partial degradation |
| 5 | Low-Moderate | Noticeable inconvenience |
| 4 | Low | Minor customer annoyance |
| 3 | Very Low | Small effect |
| 2 | Minimal | Barely noticeable |
| 1 | None | No customer impact |
How AIAG-VDA Determines Severity Ratings
AIAG-VDA evaluates Severity based on the effect of the failure mode rather than the cause of the failure.
This distinction is critical. Teams frequently lower Severity because they believe a failure is unlikely. That logic belongs in Occurrence, not Severity.
Maintaining this separation improves consistency across projects and ensures that Action Priority decisions remain objective.
Severity Rating Decision Framework
When assigning Severity ratings, ask the following questions in order:
- Can the failure create a safety risk?
- Can it violate legal or regulatory requirements?
- Does the customer lose a critical function?
- Does product performance significantly degrade?
- Is the impact mainly cosmetic or convenience-related?
Using a structured framework reduces subjectivity and prevents rating inflation during workshops.
Severity Rating Examples
| Failure Mode | Effect | Severity |
|---|---|---|
| Brake failure | Loss of vehicle braking | 10 |
| Battery thermal event | Safety risk | 10 |
| Water ingress | Product malfunction | 8 |
| Loose fastener | Noise and vibration | 6 |
| Cosmetic scratch | Appearance issue | 3 |
| Packaging defect | Minor inconvenience | 2 |
Severity 8 vs Severity 9 vs Severity 10
One of the most difficult tasks during FMEA workshops is distinguishing between the highest Severity levels.
- Severity 10 generally involves safety hazards or regulatory non-compliance.
- Severity 9 typically represents complete loss of an essential product function.
- Severity 8 often causes major customer dissatisfaction without direct safety implications.
Teams should document their reasoning when assigning Severity 8, 9 or 10 because these ratings often receive increased scrutiny during audits and customer reviews.
Severity Rating Examples by Industry
| Industry | Failure Example | Severity |
|---|---|---|
| Automotive | Brake system failure | 10 |
| Automotive | Interior trim scratch | 3 |
| Medical Device | Incorrect dosage delivery | 10 |
| Electronics | Power supply failure | 9 |
| Machining | Critical bore out of tolerance | 8 |
| Injection Molding | Minor flash on hidden feature | 2 |
| Consumer Products | Packaging tear | 2 |
Can Severity Be Reduced?
This is one of the most misunderstood concepts in FMEA.
Detection controls may reduce risk exposure but they do not change the consequence experienced by the customer if the failure escapes.
Severity can only be reduced by changing the design, process or resulting effect itself.
Why Inspection Does Not Change Severity
| Action | Changes Severity? | Changes Detection? |
|---|---|---|
| Add camera inspection | No | Yes |
| Increase sampling frequency | No | Yes |
| Add poka-yoke detection | No | Yes |
| Redesign component | Yes | Possibly |
| Add fail-safe feature | Yes | Possibly |
Relationship Between Severity, Occurrence and Detection
Severity is only one component of overall risk assessment. AIAG-VDA combines Severity, Occurrence and Detection to determine Action Priority.
Severity and Action Priority
Severity has a disproportionate influence on Action Priority decisions.
High Severity values frequently produce High Action Priority outcomes even when Occurrence remains relatively low.
Learn more in the Action Priority Guide.
Severity Rating Calibration Best Practices
- Use documented company examples.
- Review historical customer complaints.
- Review warranty and field-return data.
- Use cross-functional teams.
- Avoid political pressure.
- Maintain consistency across programs.
The goal is not perfect precision. The goal is consistent risk evaluation across all FMEAs.
Common Severity Rating Mistakes
- Rating based on occurrence instead of consequence.
- Reducing Severity after adding inspections.
- Using politics instead of objective criteria.
- Confusing customer impact with internal inconvenience.
- Ignoring safety implications.
- Ignoring regulatory consequences.
- Using different logic between projects.
Audit Perspective: What Auditors Look For
During IATF 16949 and customer audits, reviewers frequently examine high-Severity rows first.
- Consistency of rating logic.
- Evidence supporting Severity assignments.
- Alignment between FMEA and Control Plan.
- Appropriate actions for high-risk items.
- Traceability of design or process changes.
Weak justification for Severity ratings is a common source of audit findings.
Key takeaways
- Severity is about the customer effect, not how often it happens.
- Severity 9–10 means safety or regulatory non-compliance — these rows always become High AP.
- Severity 7–8 means loss of primary function — usually High or Medium AP.
- Only a design change can lower Severity; detection improvements cannot.
- Align Severity anchors across DFMEA and PFMEA so handoffs stay coherent.
Severity in the Qhubio knowledge graph
How Severity connects to other FMEA concepts, standards, examples and software.
Learning path
Three tiers, automatically derived from the Qhubio knowledge graph. The tier containing this guide is highlighted.
Further reading
Curated next steps — methodology guides, worked examples, and the relevant tool.
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