How the OEE calculator works
OEE compares the time you spent making good product at the ideal rate with the time you planned to produce. The calculator takes five numbers and works out three factors, then multiplies them.
The result is the same as fully productive time ÷ planned production time. Splitting it into three factors keeps the loss categories apart, which is what makes it useful for improvement. The full method is in how to calculate OEE.
Availability = run time ÷ planned time. Performance = (ideal cycle time × total units) ÷ run time. Quality = good units ÷ total units.
Worked example
Load the example to see it. A packaging line is planned for 450 minutes, stops for 60, has an ideal cycle of 0.5 minutes per unit and makes 720 units, of which 690 are good.
| Factor | Calculation | Result |
|---|---|---|
| Availability | 390 ÷ 450 | 86.7% |
| Performance | (0.5 × 720) ÷ 390 | 92.3% |
| Quality | 690 ÷ 720 | 95.8% |
| OEE | 345 ÷ 450 | 76.7% |
How to read your result
The lowest of the three factors shows which kind of loss is largest. OEE is loss evidence, not a target: recovering a loss only helps if it is at the constraint. See OEE loss analysis and why OEE improved but throughput did not.
| Lowest factor | The loss is usually | Start with |
|---|---|---|
| Availability | Breakdowns, changeovers and waiting | Downtime Pareto and SMED |
| Performance | Small stops and running below the ideal rate | Production downtime tracking |
| Quality | Scrap, rework and startup rejects | Root-cause analysis |
Common mistakes with an OEE calculator
Most disagreements about OEE come from the inputs, not the arithmetic.
- Using the average cycle time instead of the best demonstrated rate, which hides performance loss.
- Including breaks and planned stops in planned production time, which shows them as availability loss.
- Counting reworked units as good, which hides quality loss.
- Entering a stop threshold that ignores short stops, then wondering why performance looks too good.
- Comparing your score with another plant that defines planned time differently.