How to use the oee calculator
- Enter the planned production time in minutes and the downtime inside it.
- Enter the ideal cycle time in seconds per unit, the fastest steady time the line can make one.
- Enter the total units made and the good units.
- Read the headline OEE and the three parts, availability, performance and quality, to see where the time was lost. Copy, Print or export the CSV.
Formula
availability = (planned time - downtime) / planned time
performance = (ideal cycle time x total units) / run time
quality = good units / total units
OEE = availability x performance x quality
Times are converted to minutes. OEE also equals good units times the ideal cycle time, divided by the planned time. If performance would be above 100%, the page asks you to check the cycle time and counts.
One 8 hour shift
Planned time is 480 minutes with 47 minutes of downtime, so the machine ran 433 minutes and availability is 433 / 480 = 90.2%. At an ideal 30 seconds per unit, 780 units should take 390 minutes, so performance is 390 / 433 = 90.1%.
Of 780 units, 738 were good, so quality is 94.6%. OEE is 0.9021 x 0.9007 x 0.9462 = 76.9%, which matches 738 x 30 seconds / 60 / 480 minutes = 0.76875.
Reading the three parts
Availability shows time lost to stops, such as breakdowns and changeovers. Performance shows time lost to running slower than the ideal rate, including small stops. Quality shows output lost to rejects and rework. Because they multiply, a modest loss in each part adds up to a larger loss overall.
The part with the lowest percentage is usually the best place to start looking, but the cost of fixing each one is different, so use the numbers as a guide and not a verdict.
Definitions matter
OEE depends on what you count as planned time, what counts as downtime and how the ideal cycle time was chosen. A generous ideal makes performance look poor and a cautious one makes it look good. Compare OEE only against numbers that use the same definitions, and write them down.
No target is built in, because good values differ by process and industry. For related inventory and operations tools, see the economic order quantity calculator, the reorder point calculator and the inventory turnover calculator.
Assumptions and limits
- Downtime must be less than planned time, and good units cannot exceed total units.
- At least one unit must be made so that performance and quality can be measured.
- Performance above 100% is refused, because it usually means the ideal cycle time or a count is wrong.
- Nothing is stored or uploaded, and no benchmark is built in.
Frequently asked questions
How do you calculate OEE?
Multiply availability, performance and quality. Availability is run time over planned time, performance is ideal cycle time times total units over run time, and quality is good units over total units.
What is a good OEE?
This page does not set a target. Good values depend on the process and on how planned time and the ideal cycle time are defined, so compare with your own past figures using the same definitions.
What is the ideal cycle time?
It is the fastest steady time to make one unit under good conditions, such as the rated speed of the machine. Using an average instead of the fastest rate hides performance losses.
Why did the page refuse my numbers?
Performance came out above 100%, meaning the units you made would have taken less time than the machine ran at the ideal rate. Check the cycle time, the unit count and the run time.