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OEE calculator
Overall equipment effectiveness: the share of planned production time that made good parts at the ideal rate. Enter one shift, day or week.
How it is calculated
Where the time goes: the six big losses
| OEE factor | Loss | Examples |
|---|---|---|
| Availability | Equipment failure; setup and adjustment | Breakdowns, changeovers, waiting for material or an operator |
| Performance | Idling and minor stops; reduced speed | Jams and short stops nobody logs, running below the ideal rate |
| Quality | Process defects; startup rejects | Scrap, rework, parts made while the process warms up |
Attack the biggest loss first. The calculator turns each factor into minutes so the losses can be compared on one scale.
Mistakes to avoid
- A slow ideal cycle time. Performance above 100% means the ideal is set too slow.
- Counting reworked parts as good. Good count is right first time.
- Hiding changeovers in planned time. Changeovers are availability loss. They are often the biggest one, and the first target for SMED.
Read more: Takt time · The 8 lean wastes · Theory of constraints · Availability and maintainability
FAQ
What is a good OEE score?
85% is the figure most often quoted as world class, from the early TPM literature. Many plants that measure honestly for the first time land well below that. The number matters less than the trend and which of the three losses is biggest.
What should count as planned production time?
Shift time minus planned stops such as breaks, meetings and planned maintenance. Everything else that stops the line (breakdowns, changeovers, waiting for material) is downtime and counts against availability.
What ideal cycle time should I use?
The fastest rate the equipment can sustain for this product, from the nameplate or the best demonstrated rate. If you use the average rate, performance looks close to 100% and the slow-cycle loss disappears from view.
How is OEE different from availability or utilization?
Availability only sees stops. OEE also sees slow running (performance) and scrap or rework (quality). A line can be available 95% of the time and still have an OEE of 60%.
Can I average OEE across machines?
Not as a simple average. Add up the fully productive time and the planned time across machines (or weight by planned time). A simple average gives a small machine the same weight as a large one.
This shows up on the exams as a calculation question. Practice it with new numbers every time, and every wrong answer explained.
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