What is a good or bad RPN?

There is no universal cut-off. The RPN ranks failure modes within one analysis, from 1 to 1,000, and the team works on the highest first. Many teams also act on any failure mode with a severity of 9 or 10, whatever its RPN, because a rare catastrophic failure can score lower than a frequent minor one.

Why is a high detection score bad?

In IHI’s FMEA tool the detection score is the likelihood that the failure would NOT be detected: 10 means it would almost certainly slip through. A high score therefore raises the RPN, just like a high occurrence or severity score.

How is FMEA different from root cause analysis?

FMEA is proactive: a team studies a process before something goes wrong and asks how it could fail. Root cause analysis is reactive: it investigates an event that already happened, such as a sentinel event. Quality programs use both.

Free tool · CPHQ® exam topic

FMEA risk priority number calculator

Score each failure mode from 1 to 10 for occurrence, detection and severity. The tool multiplies them into a risk priority number (RPN) and ranks your list.

Priority order

1.Pump programmed with the wrong rate225
2.Dose transcribed wrong from the order216
3.Blood glucose check done late108
4.Wrong patient selected at bedside scan96

Occurrence: 1 = very unlikely, 10 = very likely to occur
Detection: 1 = very likely to be caught, 10 = very unlikely to be caught
Severity: 1 = no harm, 10 = severe harm or death if it happens

Formula

In IHI’s FMEA tool, each failure mode gets three scores from 1 to 10: the likelihood of occurrence, the likelihood that it would not be detected, and the severity of harm if it happens. The risk priority number is their product:

RPN = occurrence × detection × severity, from 1 to 1,000.

Worked example

A team maps the steps of an IV insulin infusion and lists what could go wrong at each one. The pump programming error scores 5 for occurrence, 5 for detection and 9 for severity, so its RPN is 5 × 5 × 9 = 225, the highest on the list. The team designs a fix (for example, smart-pump drug libraries with hard limits), then rescores the failure mode to confirm the RPN dropped.

Running an FMEA

Pick a high-risk process and gather a team that does the work.
Map the process steps.
For each step, list failure modes, their causes and their effects.
Score occurrence, detection and severity, and calculate the RPN.
Act on the highest RPNs (and any severity of 9 or 10), then rescore.

The scores in the example are illustrative. Agree on written definitions for each score before the team starts, so ratings are consistent.

Test yourself: a CPHQ-style question

Which element is NOT typically included in an FMEA risk priority number (RPN) calculation?

Severity
Occurrence
Detection
Cost of failure

Show answer

D. Cost of failure

The RPN is calculated by multiplying severity × occurrence × detection, each scored on a 1–10 scale. Cost of failure is not part of the standard RPN formula.

Questions like this come up in the Patient Safety domain of the CPHQ® exam. The 249 questions in the app each come with a written explanation.

FAQ

What is a good or bad RPN?: There is no universal cut-off. The RPN ranks failure modes within one analysis, from 1 to 1,000, and the team works on the highest first. Many teams also act on any failure mode with a severity of 9 or 10, whatever its RPN, because a rare catastrophic failure can score lower than a frequent minor one.
Why is a high detection score bad?: In IHI’s FMEA tool the detection score is the likelihood that the failure would NOT be detected: 10 means it would almost certainly slip through. A high score therefore raises the RPN, just like a high occurrence or severity score.
How is FMEA different from root cause analysis?: FMEA is proactive: a team studies a process before something goes wrong and asks how it could fail. Root cause analysis is reactive: it investigates an event that already happened, such as a sentinel event. Quality programs use both.

Sources

Institute for Healthcare Improvement. Failure Modes and Effects Analysis (FMEA) Tool

Checked against these sources on October 29, 2026. For education and CPHQ® exam preparation only, not a substitute for your organization’s policies, official measure specifications or professional judgment. Calculations run in your browser; nothing you enter is sent anywhere.