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OEE calculator
Enter one run's planned time, stops, ideal cycle time and piece counts; get Overall Equipment Effectiveness and the three losses behind it.
Planned production time excludes scheduled breaks and periods with no orders; downtime is every stop inside that time, planned changeovers included.
How OEE is calculated
OEE (Overall Equipment Effectiveness) multiplies three ratios. Availability is run time ÷ planned production time, where run time is planned time minus stops. Performance is (ideal cycle time × total pieces) ÷ run time, so it captures slow cycles and short stops. Quality is good pieces ÷ total pieces. OEE = availability × performance × quality, which simplifies to good pieces × ideal cycle time ÷ planned production time: the share of planned time spent making good parts at full speed.
Example: a shift has 420 minutes of planned time and 47 minutes of stops, leaving 373 minutes of run time, so availability is 88.8%. With an ideal cycle of 1 second, 19,271 pieces need 321.2 minutes, so performance is 321.2 ÷ 373 = 86.1%. Of those pieces 18,848 are good, a quality rate of 97.8%. OEE is 0.888 × 0.861 × 0.978 = 74.8%. At full effectiveness the shift could have made 25,200 good pieces, so about 6,350 were lost.
| Availability | Performance | Quality | OEE |
|---|---|---|---|
| 90% | 95% | 99.9% | 85.4% |
| 90% | 90% | 98% | 79.4% |
| 85% | 85% | 95% | 68.6% |
| 80% | 75% | 95% | 57.0% |
| 70% | 70% | 90% | 44.1% |
What the score tells you
The 85% world-class figure goes back to Seiichi Nakajima's work on Total Productive Maintenance, built from 90% availability, 95% performance and 99.9% quality. Many discrete manufacturers measure around 60%, which means a large share of planned capacity is still available without buying another machine.
The headline number matters less than the factor dragging it down. Low availability points to breakdowns and long changeovers, where SMED and preventive maintenance help. Low performance points to minor stops, jams and running below rated speed, which operators often stop noticing. Low quality points to scrap, rework and start-up rejects after changeovers.
Two mistakes distort OEE. Setting the ideal cycle time to a comfortable average instead of the true design rate inflates performance, sometimes past 100%. Comparing OEE between machines that make different parts is also misleading; it is best used to track the same asset over time. OEE measures equipment, not people, so it should not be used as an operator scorecard.
Frequently asked questions
What is a good OEE score?
85% is widely cited as world-class for discrete manufacturing, 60% is common, and 40% or lower is typical when a plant first starts measuring. Trend over time matters more than the absolute number.
Are planned changeovers counted as downtime in OEE?
Yes. Changeovers and setups happen during planned production time, so they reduce availability. Only time with no production scheduled, such as breaks or no orders, is left out.
Why is my performance above 100%?
The ideal cycle time entered is slower than what the machine actually achieved. Use the fastest cycle time the equipment can sustain for that part, usually the nameplate or validated rate.