IEC 62061 vs ISO 13849: Which Machinery Safety Standard Should You Use?

Choose ISO 13849 when your safety function is lower in complexity or relies on non-electrical technology like pneumatics, hydraulics, or mechanical guarding. Choose IEC 62061 when the function is complex, software-driven, or part of a larger programmable electronic safety system. Both standards cover the safety-related parts of machinery control systems. They just measure the result differently: ISO 13849 uses Performance Level, IEC 62061 uses SIL.

That answer is enough to get most teams pointed in the right direction. The rest of this post explains why the two standards exist, how their metrics relate, and what to do when one machine needs both.

Two Standards, One Problem

Both ISO 13849 and IEC 62061 answer the same engineering question: how much can you trust the safety-related parts of a machine’s control system to do their job when a hazard appears?

They came from different worlds. ISO 13849 grew out of the machinery safety tradition and the older category-based approach (the B, 1, 2, 3, 4 categories many engineers still reference out of habit). It was built to handle any technology a machine builder might use, so it covers electrical, electronic, hydraulic, pneumatic, and mechanical systems under one method.

IEC 62061 came from the functional safety lineage of IEC 61508, the parent standard for electrical and electronic systems. It applies the SIL concept to machinery, scaled to the SIL 1 through SIL 3 range that machinery applications actually need. Its home turf is electrical, electronic, and programmable electronic control.

So you have two valid roads to the same destination. The standard you pick shapes the math you do, the evidence you produce, and how an assessor reads your safety case.

How the Metrics Differ

ISO 13849 expresses the outcome as a Performance Level, ranked PLa (lowest) through PLe (highest). The calculation combines four inputs: the architecture category, the mean time to dangerous failure (MTTFd), the average diagnostic coverage (DCavg), and common cause failure (CCF). For many single-channel or simply redundant architectures, this is a fast, well-bounded calculation.

IEC 62061 expresses the outcome as a SIL, from SIL 1 to SIL 3 in the machinery context. It uses a probabilistic failure model closer to IEC 61508, accounting for the probability of dangerous failure per hour, hardware fault tolerance, and the safe failure fraction. That extra structure pays off when a safety function has real software content or a complex architecture, where the simpler category method starts to strain.

Here is the side-by-side view.

How Performance Level Maps to SIL

Because both scales rank the same thing (how much risk reduction the safety function delivers) there is an approximate correspondence between them.

• PLa and PLb sit near the bottom of the risk-reduction range, below or around SIL 1

• PLc and PLd map to roughly SIL 1 and SIL 2

• PLe corresponds to roughly SIL 3

Treat that mapping as a translation aid, not a calculation shortcut. The two standards quantify risk reduction with different math, so a PLd result is not literally a SIL 2 result. The correspondence helps you talk across teams and compare requirements, but each safety function still gets evaluated against the standard you chose for it.

The Standards Are Converging

The split between these two standards has frustrated engineers for years, and the standards bodies know it. The 2021 update to IEC 62061 broadened its scope beyond purely electrical and electronic systems and pulled its structure closer to ISO 13849.

That update is one step in a longer effort to harmonize the two. A merged machinery safety standard has been in the works, intended to fold both the Performance Level approach and the SIL approach into a single framework. It is not finished, and you still design to the current standards today. But the direction of travel is clear: the wall between the two methods is coming down. Designing your safety case so it can carry either metric is a reasonable hedge against that change.

Choosing for Your System

The decision usually comes down to two questions: what technology does the safety function use, and how complex is it?

Reach for ISO 13849 when:

• The function uses non-electrical technology (pneumatic interlocks, hydraulic valves, mechanical guarding)

• The architecture is straightforward and not heavily software-driven

• You want the most direct calculation path for a well-understood function

• Your machine and its customers are already working in the Performance Level world

Reach for IEC 62061 when:

• The safety function has meaningful software or firmware content

• The architecture is complex or high-functionality

• The function is part of a larger programmable electronic safety system

• You are already working in a SIL framework elsewhere in the system and want consistency

And here is the case the brief gets wrong: it is not always one or the other. A single machine often mixes technologies. You might have a pneumatic guard interlock that fits ISO 13849 cleanly sitting next to a programmable electronic safety controller that belongs under IEC 62061. Picking each standard where it fits is legitimate. The real difficulty is keeping both frameworks straight across one safety case, especially once the hazard analysis drives a dozen safety functions with different metrics attached to each.

Working in Both Frameworks Without the Spreadsheet Tax

This is where the manual approach breaks down. When ISO 13849 functions live in one tool, IEC 62061 functions live in another, and the overall safety argument lives in a Word document, every change forces a reconciliation pass across all three. That tracking overhead is part of why roughly 60% of safety engineering time gets spent on documentation rather than design.

ASAP supports both ISO 13849 and IEC 62061 in one platform. A team can work in Performance Level for the pneumatic and mechanical functions, work in SIL for the programmable electronic functions, and keep every function traceable to the same hazard analysis and the same safety case. The reliability modeling handles both the category-based calculation and the probabilistic SIL calculation, so mixed-technology machinery does not mean mixed-up documentation.

Fennec's specified ASAP tools are qualified by TÜV Rheinland as Tool Class 2 (T2) offline support tools under IEC 61508-3:2010, Clause 7.4.4. The qualification gives project teams independent evidence about the named tools. It does not qualify the full lifecycle or remove the need to review calculations and traceability against the applicable standard.