Free FMEA RPN Calculator: Severity, Occurrence, Detection

Rate your failure modes

The rows below are example data for a food packaging line. Edit them, add rows, or paste CSV (step, failure mode, effect, S, O, D).

Paste CSV instead

Highlight the top by RPN, and any severity of or more.

Ranked by RPN

Running a full improvement project? The full DMAIC toolkit with 54 tools includes FMEA with automatic RPN alongside the charter, SIPOC, value stream map, fishbone, Gage R&R, control plan and A3, with printable reports. It works offline in your browser. This free calculator stays free.

What is FMEA?

Failure Mode and Effects Analysis (FMEA) is a structured way for a team to ask, step by step: how could this process or product fail, what would happen if it did, why would it happen, and would we catch it? Each failure mode gets three ratings, and the result is a ranked list showing where to act first. It is used in the Analyze and Improve phases of DMAIC, in product design (DFMEA) and when a process is set up or changed (PFMEA).

How RPN is calculated

Severity (S), 1 to 10: how serious the effect is for the customer or the next step. 10 is hazardous or a regulatory failure without warning.
Occurrence (O), 1 to 10: how likely the cause is to happen. 1 is remote, 10 is almost certain.
Detection (D), 1 to 10: how likely current controls are to miss it before it reaches the customer. 1 means it is almost certain to be caught, 10 means there is no realistic way to detect it.
RPN = S × O × D, from 1 to 1,000.

Worked example (example data)

In the example, a heat sealer whose temperature drifts low is rated S 8, O 4, D 6, for an RPN of 192, the highest on the list. A skipped metal detector check scores only 100 (S 10, O 2, D 5), below the top three, but its severity is 10, so the calculator still highlights it. A team would add a temperature alarm or interlock on the sealer, make the metal detector check impossible to skip, re-rate both after the change and record the new RPNs.

Why RPN alone can mislead

Equal RPNs, unequal risk. S 10 × O 2 × D 3 and S 3 × O 4 × D 5 both give 60. The first could hurt someone. That is why this tool highlights high-severity rows regardless of RPN.
The scale is ordinal. An RPN of 200 is not "twice as risky" as 100. Use it to rank and discuss, not as a precise measurement.
Fixed thresholds invite gaming. A rule such as "act on anything over 100" encourages rating just under the line. Rank, then act on the top items and every high-severity item.
Newer guidance uses Action Priority. The 2019 AIAG and VDA FMEA handbook replaced RPN thresholds with an Action Priority table that weights severity first. RPN is still widely used and easy to explain, so it remains a good starting point.

Tips for a useful FMEA

Do it as a team that includes people who run the process, not one person at a desk.
Agree on the rating scales before you start, and write them down, so ratings stay consistent.
Rate the cause as it is today, with current controls, not as you hope it will be.
Reducing occurrence (preventing the cause) usually beats improving detection (inspecting harder).
Assign an owner and a date for each action, then re-rate after the change.

Privacy

All calculations are done with JavaScript on this page. Nothing you type is sent to a server or stored.

Also free: the Pareto chart maker and the control chart maker. See the template store for paid templates and apps.

Made by a Six Sigma Master Black Belt with 17 years of Lean Six Sigma process improvement experience.