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Overall equipment effectiveness (OEE)

OEE is availability times performance times quality. It tells you what share of planned production time a machine spends making good parts at its ideal speed.

The result depends on what you count as planned time and which ideal cycle time you pick. Compare a machine with itself over time, not with another plant.
In the standard Not defined in EN 13306.
German Gesamtanlageneffektivität (OEE)
Also called OEE 2 in the SMRP guideline, as Gulati reports it. Not the same as TEEP, which SMRP calls OEE 1

Is OEE availability the same as availability?

No. EN 13306 defines availability (4.7) for a machine that gets everything it needs from outside maintenance: material, power, staff. A missing order does not lower it. OEE availability compares the time the machine runs with the time it was scheduled to run (Gulati). Any stop inside that time lowers it, whatever the cause.

How do you calculate OEE?

OEE = availability × performance × quality

Availability = run time / planned production time
Performance  = (ideal cycle time × total count) / run time
Quality      = good count / total count
  • Planned production time: the hours the plant schedules the machine to produce. Breaks and unscheduled shifts stay out.
  • Run time: planned production time minus every stop. This page counts planned changeovers as stops. Some sites do not, and their OEE reads higher.
  • Ideal cycle time: the fastest cycle the machine is designed for or has held over a long run.
  • Total count and good count: all parts made, and the parts that pass inspection. Rework and scrap are not good parts.

The three terms share their numerators and denominators, so they collapse into one check: good count × ideal cycle time / planned production time.

The 19.55 lost hours split three ways: 6 h of stops, 11.5 h of slow running, and 2.05 h of scrap. The stop log shows only the first 6 h. The data cannot say whether the 11.5 h come from slow cycles or short stops nobody logged; the controller's cycle data can.

What is a good OEE?

We found no public value that holds across plants. EN 13306 does not mention OEE. Gulati calls 85% "not uncommon" as a benchmark target and names no source. Wireman reports observed values from under 20% to over 85%. He adds that 85% costs too much for some processes and is too low for others. The often-quoted "world-class 85 percent" has no traced source: Is world-class OEE really 85 percent? follows the trail.

When does OEE mislead?

  • Different definitions. Planned time, ideal cycle time, and the treatment of changeovers move the number. Two plants with the same OEE may measure different things. TEEP divides by all calendar time instead of planned time (Gulati).
  • A soft ideal cycle time. If you set the ideal to what the machine usually does, performance reads near 100% and hides the speed loss. Use the design speed or the best speed held over a long run.
  • Excluded stops. Leaving changeovers out of planned time raises OEE and hides a loss that teams can often cut.
  • Short stops. A jam cleared in 30 seconds, twenty times a shift, lowers performance, not availability. Gulati lists minor stoppages as a performance loss. Count them from the machine controller or a part counter, not from a paper log.
  • Product mix. A machine that runs only its easiest product scores higher and may serve customers worse.

We recommend you use OEE to find the largest of the three losses, then work on that loss. This follows principle 10 of the Maintenance Manifesto, "Manage the work, not the metric". The number only shows whether the work paid off. Wireman names the same trap: a benchmark turned into a goal pulls effort toward the number. Gulati adds that production and maintenance both move OEE, so both should read it.

Sources

  • Ramesh Gulati, Maintenance and Reliability Best Practices, 3rd ed., Industrial Press, 2021, chapter 7 (OEE, TEEP, SMRP naming, the answer to self-assessment question 4).
  • Terry Wireman, Benchmarking Best Practices in Maintenance, Reliability and Asset Management, 3rd ed., Industrial Press, 2015, chapter 12 (equipment performance, Figure 12-7) and chapter 2 (traps to benchmarking).
  • EN 13306:2017, Maintenance: Maintenance terminology, CEN, 2017. Clauses 4.7 and 4.9. This page explains the standard in our own words; the standard is the authority. Buy it as DIN EN 13306:2018-02 from DIN Media.
  • Maintenance Manifesto, 2025, principle 10.