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OEE Six Big Losses Reference Table

OEE falls short of 100 percent because of equipment losses. The six big losses group them into availability, performance and quality. This table maps each loss to its OEE factor and shows what to log, where the data comes from and the usual countermeasure.

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Loss	OEE factor	Loss type	Example	Typical data source	Typical countermeasure
1. Equipment failure (breakdowns)	Availability	Downtime	Spindle bearing failure stops the machine for 3 hours.	Downtime log with reason code, maintenance work orders.	Planned and autonomous maintenance, condition monitoring, spares.
2. Setup and adjustments	Availability	Downtime	Changeover and first piece approval between part numbers.	Setup start and end times, routing setup time.	SMED, standardized tooling, preset tools.
3. Idling and minor stops	Performance	Speed loss	Sensor jam cleared by the operator in under 5 minutes.	Machine signals, short stop counter, operator comments.	Cleaning, inspection, small design fixes, root cause of jams.
4. Reduced speed	Performance	Speed loss	Machine run at 80 percent of ideal rate to avoid tool wear.	Actual versus ideal cycle time per part.	Tool and parameter optimization, equipment restoration.
5. Process defects (scrap and rework)	Quality	Quality loss	Parts scrapped for out of tolerance bores.	Scrap postings, inspection results, NCRs.	Poka-yoke, process capability study, standard work.
6. Reduced yield (startup rejects)	Quality	Quality loss	First parts after startup scrapped until process stabilizes.	Scrap coded to startup, warm-up logs.	Warm-up routines, startup standards, stable settings.
Planned downtime (not in OEE)	Excluded from OEE, included in TEEP	Scheduling	Scheduled preventive maintenance or break periods.	Shift calendar, maintenance plan.	Plan around demand; reduce through faster PM.
No demand or no operator	Excluded from OEE, included in TEEP	Scheduling	Machine idle on a shift with no orders.	Calendar versus scheduled production time.	Load leveling, cross training, schedule review.
Material shortage	Availability	Downtime	Line stops while waiting for a component.	Downtime reason, material availability check.	Kanban replenishment, supermarket, supplier delivery review.
Tool change	Availability	Downtime	Insert change interval stops the cycle.	Tool life counters and downtime reason.	Tool life management, quick change holders.

The six big losses come from TPM literature. Whether a loss counts as planned downtime or available time depends on how your organization defines scheduled production time. Agree the definition before comparing OEE numbers across sites.

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How to use the table

Use it to design downtime reason codes. Each reason code should roll up into exactly one of the six losses, otherwise your Pareto chart will mix categories. Search for the loss you suspect, check the data source column against what your MES or ERP actually captures, and note gaps. Export to Excel and use it as the master list for operator tablets or paper downtime sheets.

How losses map to OEE

OEE equals availability times performance times quality. Losses 1 and 2 reduce availability. Losses 3 and 4 reduce performance. Losses 5 and 6 reduce quality. Availability is run time divided by planned production time. Performance is ideal cycle time times total count divided by run time. Quality is good count divided by total count. The mapping tells you which factor to examine first when OEE is low.

Availability losses: breakdowns, setups, material waits, tool changes.
Performance losses: minor stops and reduced speed.
Quality losses: scrap, rework and startup rejects.

Reading and acting on the data

Collect at least two to four weeks of downtime data before drawing conclusions, then rank losses by minutes lost. Minor stops are often the largest hidden loss because they are too short to be logged by hand. If your data shows large unexplained downtime, the first countermeasure is better capture, not more analysis. Attack the largest loss with a focused improvement team, and re-measure after the change.

Common mistakes

Do not count planned stops against OEE unless you are measuring TEEP. Avoid a reason code list with a long tail of vague codes such as Other; it should be a short list of eight to fifteen codes that operators actually choose. Finally, compare OEE only between machines with the same ideal cycle time definition, or the numbers will mislead.

Frequently Asked Questions

What are the six big losses in OEE?

Equipment failure, setup and adjustments, idling and minor stops, reduced speed, process defects, and reduced yield during startup. The first two reduce availability, the next two reduce performance, and the last two reduce quality.

Which loss is usually largest?

It varies by plant. Many sites find that setup and minor stops are larger than breakdowns once they measure properly. Minor stops are often invisible until a machine signal or short stop counter is added, so measure before assuming.

How many downtime reason codes should I use?

A short list of about eight to fifteen codes that map clearly to the six big losses works well. Too many codes slow the operator and lower data quality. Each code should belong to exactly one loss category.

What is the difference between OEE and TEEP?

OEE measures performance against planned production time. TEEP, total effective equipment performance, measures against all calendar time, so planned downtime and no demand periods also count as loss. TEEP shows how much capacity is unused.

If your downtime and scrap already sit in an ERP or MES, we can help you query them in plain language and keep the analysis on your own servers.

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