The short answer
Action Priority (AP) is how the AIAG-VDA FMEA Handbook (2019) ranks which FMEA rows need action first. It replaced the old Risk Priority Number (RPN). Understanding Quality Institute teaches AP as the recommended method; RPN is covered here so you can read older FMEAs and explain the switch.
| Action Priority (recommended) | RPN (legacy) | |
|---|---|---|
| How it works | Look up S, O and D in the AIAG-VDA table | Multiply: S × O × D |
| Result | High, Medium or Low | A number from 1 to 1,000 |
| Weighting | Severity first, then Occurrence, then Detection | All three ratings count equally |
| What it tells you | "This row must / should / could get an action" | "This number is bigger than that one" |
| Where you'll see it | AIAG-VDA FMEAs (DFMEA and PFMEA) | Older FMEAs and some customer forms |
How the old RPN method worked
Each FMEA row gets three ratings from 1 to 10: Severity (how bad the effect is), Occurrence (how likely the cause is) and Detection (how likely you are to miss it). RPN multiplies them:
RPN = S × O × D (1 to 1,000)
Teams sorted the list by RPN and worked from the top, often with a cut-off like "act on anything over 100." It was quick and easy to explain, and that's why it lasted so long. The trouble is what the multiplication hides.
Why RPN was dropped
1. Very different risks get the same number
All three rows below have an RPN of 80. Only one of them involves a safety effect.
| S / O / D | AP | Legacy RPN | What it describes |
|---|---|---|---|
| 10 / 4 / 2 | H | 80 | Safety effect, cause happens now and then, good inspection |
| 4 / 5 / 4 | L | 80 | Moderate annoyance, moderate occurrence, good inspection |
| 2 / 10 / 4 | L | 80 | Minor cosmetic issue that happens all the time |
RPN says these are equal. Action Priority puts the safety row at High and the other two at Low.
2. Thresholds let serious risks slip through
With an "act above 100" rule, a 9 / 6 / 1 row (RPN 54) gets ignored, while a 5 / 5 / 6 row (RPN 150) gets the team's attention. Action Priority rates the first one High (a serious effect with a fairly likely cause, where everything rides on inspection) and the second one Low.
3. The ratings aren't really numbers you can multiply
S, O and D are rankings, not measurements. A Detection of 6 isn't "twice as bad" as a 3. Multiplying rankings creates false precision. Only 120 different RPN values are even possible between 1 and 1,000, and the gaps between them mean nothing.
4. It rewards inspection over prevention
Adding another inspection lowers D, and the RPN drops just as much as it would if you fixed the cause. Action Priority looks at Occurrence before Detection, so fixing the cause (better prevention) is what moves a row down most reliably.
How Action Priority works
AP doesn't calculate anything. The handbook groups each rating into bands and gives every combination a priority:
| Rating | Bands used by the AP table |
|---|---|
| Severity | 9–10 · 7–8 · 4–6 · 2–3 · 1 |
| Occurrence | 8–10 · 6–7 · 4–5 · 2–3 · 1 |
| Detection | 7–10 · 5–6 · 2–4 · 1 |
You read the table in order: find the Severity band, then the Occurrence band within it, then the Detection band. The same table is used for both DFMEA and PFMEA. (FMEA-MSR, the supplemental FMEA for monitoring and system response, has its own table.)
What High, Medium and Low mean
- High: the team needs to identify an action to improve prevention or detection, or justify and document why the current controls are adequate.
- Medium: the team should identify an action, or document why not.
- Low: the team could identify an action.
The handbook is clear that AP is a priority for action, not a ranking of how risky the product is. It also recommends that, at a minimum, Severity 9–10 items rated High or Medium are reviewed by management.
Patterns worth knowing
You still need the table for real work, but these patterns hold across it:
- Severity 9–10 with Occurrence 6 or higher is always High, however good the detection.
- Severity 9–10 with Occurrence 4–5 is High unless Detection is 1, which brings it to Medium.
- Occurrence 1 is always Low, even for Severity 10, because prevention makes the cause virtually impossible. That's why honest Occurrence ratings matter.
- Severity 4–6 only reaches High when Occurrence is 8–10 and Detection is 5 or worse.
- Severity 2–3 is never High, and Severity 1 is always Low.
Example combinations
These rows show Action Priority with the legacy RPN beside it for comparison. The AP values follow the 2019 AIAG-VDA table. For your own FMEAs, always use the table in your copy of the AIAG-VDA handbook and your customer's requirements.
| S / O / D | AP | Legacy RPN | What it describes |
|---|---|---|---|
| 10 / 4 / 7 | H | 280 | The wheel-nut row from the FMEA guide, before action |
| 10 / 2 / 2 | L | 40 | Same row after error-proofing (cause fixed, interlock added) |
| 10 / 4 / 2 | H | 80 | Safety effect, moderate occurrence, good inspection |
| 4 / 5 / 4 | L | 80 | Moderate effect, moderate occurrence, good inspection |
| 2 / 10 / 4 | L | 80 | Minor effect that happens all the time |
| 9 / 6 / 1 | H | 54 | Serious effect, cause fairly likely, near-certain detection |
| 5 / 5 / 6 | L | 150 | Moderate effect, moderate occurrence, average detection |
| 10 / 1 / 10 | L | 100 | Safety effect, but prevention makes the cause virtually impossible |
| 9 / 3 / 6 | M | 162 | Serious effect, low occurrence, average detection |
| 7 / 5 / 5 | M | 175 | High effect, moderate occurrence, average detection |
Look at the RPN column alone and the 10 / 4 / 2 row (RPN 80, High) would sit below the 5 / 5 / 6 row (RPN 150, Low). The 10 / 1 / 10 row has an RPN of 100 and still comes out Low, because the cause has effectively been designed out.
How to switch from RPN to Action Priority
- Check what your customer requires. Customer-specific requirements decide which FMEA format you use and whether RPN must still appear anywhere.
- Get the handbook and its rating tables. AIAG-VDA changed the Severity, Occurrence and Detection criteria as well as the ranking method, so use the new tables. Don't just copy old ratings across.
- Update your template. Add Action Priority columns for before and after action. If you keep RPN, label it "reference only" and stop sorting by it. The free UQI worksheet is already set up this way.
- Re-rate as a team. Re-rate the rows you're bringing forward against the new criteria, starting with anything Severity 9–10. Have the people who know the process in the room.
- Work High first, then Medium. Give every action an owner and a date. Where you decide not to act on a High, write down why the current controls are adequate, and send Severity 9–10 High and Medium items for management review.
- Retire RPN thresholds. Remove "act above 100" rules from procedures, work instructions and dashboards, or they'll keep pulling the team back to the old method.
- Re-rate after actions and keep it alive. When an action is done, re-rate and update AP. Revisit the FMEA after process changes, customer complaints and every 8D.
Common mistakes when moving to AP
- Converting RPNs into AP with a formula. There's no conversion. AP comes from the three ratings, not from the RPN.
- Using old rating scales with the new table. The AP table assumes the AIAG-VDA rating criteria.
- Rating Occurrence 1 too easily. It turns any row Low, so it needs real prevention behind it.
- Treating Low as "done forever." Low means "could act." Good ideas for a Low row are still worth doing.
- Keeping an RPN sort "just in case." If the list is still sorted by RPN, the team is still using RPN.
Action Priority questions people ask
What is the difference between Action Priority and RPN?
RPN multiplies Severity × Occurrence × Detection into a number from 1 to 1,000 and treats all three ratings as equally important. Action Priority (AP), from the 2019 AIAG-VDA FMEA Handbook, looks the three ratings up in a table that returns High, Medium or Low, with Severity weighted first, then Occurrence, then Detection.
Is RPN still allowed?
AIAG-VDA FMEAs use Action Priority, not RPN. Some customers or older FMEAs still ask for RPN, so some teams keep it as a reference column. If you do, don't rank or decide actions by it. Follow your customer's specific requirements.
Does Severity 10 always mean High Action Priority?
No. Severity comes first, but the table still looks at Occurrence and Detection. For example, Severity 10 with Occurrence 1 is Low, because prevention makes the cause virtually impossible. Severity 9 or 10 with Occurrence 6 or higher is always High.
What does a High Action Priority require?
For High, the team needs to identify an action to improve prevention or detection, or justify and document why the current controls are adequate. Medium should get an action or a documented reason. Low could get an action.
Can I calculate Action Priority with a formula?
There's no multiplication. AP is a lookup in the handbook's table. In a spreadsheet it's usually done with a lookup table or nested IF formulas built from your copy of the handbook. The free UQI FMEA worksheet has AP columns for before and after action.
