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OEE Formula: A Worked Manufacturing Example
OEE is availability × performance × quality. It measures the share of planned production time equivalent to making acceptable output at the ideal equipment rate—not how busy people are.
Set the equipment boundary first
Use one machine or clearly defined line, one product basis and one period. Scheduled time is the recorded shift window. Excluded time is time you decided production was not planned; stop time is lost time within planned production. Document this convention before comparing shifts. Do not move a troublesome stop into excluded time simply to improve the number.
Total output includes good and rejected output. Good output is acceptable on the stated quality basis; avoid counting reworked items twice. The ideal rate is the equipment’s justified ideal capability for that product, not the average rate from a slow observation.
Calculate one shift, step by step
Fictional manufacturing teaching example. These figures are not ORDREL customer results.
| Input | Value | Meaning |
|---|---|---|
| Scheduled time | 480 min | One eight-hour window |
| Excluded time | 30 min | Production not planned |
| Stop time | 45 min | Stops inside planned time |
| Ideal rate | 2 units/min | Equivalent to 30 seconds/unit |
| Total output | 750 units | Including rejected units |
| Good output | 720 units | Accepted output |
Planned production time = 480 − 30 = 450 minutes. Run time = 450 − 45 = 405 minutes.
- Availability = 405 ÷ 450 = 90%.
- Performance = 750 ÷ (405 × 2) = 92.5926%.
- Quality = 720 ÷ 750 = 96%.
- OEE = 0.9 × (750 ÷ 810) × 0.96 = 80%.
Cross-check directly: good output ÷ ideal output in planned time = 720 ÷ (450 × 2) = 80%. Keep full precision until the final display. Multiplying rounded factor percentages can produce a slightly different answer.
Turn the result into a question
At the ideal rate, good output represents 720 ÷ 2 = 360 productive-equivalent minutes. The remaining 90 minutes split into 45 stop minutes, 30 speed-loss minutes and 15 quality-loss-equivalent minutes. These add to the 450 planned minutes. Quality-loss minutes are an equivalent at the ideal rate, not the actual time spent repairing defects.
This suggests investigating recorded stops first in this scenario, but severity, constraints and recoverability matter. A high score alone does not establish customer value, adequate capacity, profitability or a safe process. Do not compare unrelated products or equipment using an unweighted average of percentages.
Reproduce it in ORDREL
Open the OEE calculator. Select units/pieces and the ideal-output-per-minute basis. Enter 480 scheduled, 30 excluded, 45 stopped, rate 2, total 750 and good 720. Expect 80% OEE and the three factors above. The calculator is free on screen; saved-work, exports and reports follow the existing plan boundaries.
Use recorded stop reasons for a Pareto investigation. Keep labor minutes separate when moving to staffing: an equipment rate is not output per worker.
Common questions and mistakes
- Can performance exceed 100%? Treat that as a rate, unit or boundary problem to investigate. ORDREL flags it rather than silently capping the value.
- Is zero production always 0% OEE? With planned time and no output, OEE is zero; with no planned production, it is not defined. Missing data must not be entered as a measured zero.
- Does 80% mean the line can make 20% more immediately? No. Losses may overlap operational constraints or require investment, qualification and trials to recover.
- Should breaks be deducted twice? No. State where each break belongs in your schedule definition and use it only once.
Sources and method notes
Sources support the method definitions. Examples, interpretation and tool instructions are ORDREL teaching material, not an endorsement by the referenced organizations. See methods and corrections.