OEE Calculator
Calculate Overall Equipment Effectiveness from availability, performance and quality inputs. Enter percentages directly or use raw production data for the full breakdown.
How OEE is calculated
Overall Equipment Effectiveness is the product of three factors, each measuring a different category of production loss:
OEE = Availability × Performance × Quality
| Factor | Formula | Losses it captures |
|---|---|---|
| Availability | (Planned time − Unplanned downtime) ÷ Planned time | Equipment breakdowns; setup and adjustment time beyond standard |
| Performance | (Total parts × Ideal cycle time) ÷ Run time | Idling and minor stoppages; running below design speed |
| Quality | Good parts ÷ Total parts produced | Process defects (scrap and rework); startup/ramp-up yield losses |
Worked example
A stamping press runs one 8-hour shift. Scheduled breaks total 60 minutes, so planned production time = 420 minutes. Unplanned downtime (two breakdowns) = 60 minutes. Ideal cycle time = 0.5 min/part. Total parts produced = 600. Good parts (passed quality) = 570.
- Availability = (420 − 60) ÷ 420 = 360 ÷ 420 = 85.7%
- Performance = (600 × 0.5) ÷ 360 = 300 ÷ 360 = 83.3%
- Quality = 570 ÷ 600 = 95.0%
- OEE = 0.857 × 0.833 × 0.950 = 67.8%
Despite each individual factor looking reasonable, the multiplicative nature of OEE means the combined result is significantly lower. This is why OEE is a more demanding metric than any single factor.
OEE benchmarks
| OEE range | Rating | Typical context |
|---|---|---|
| ≥ 85% | World-class | Mature high-volume repetitive manufacturing with sustained TPM programme |
| 70–84% | Good | Well-run SME manufacturing; typical target for improvement programmes |
| 50–69% | Fair | Typical starting point when OEE is first measured; significant losses not yet addressed |
| < 50% | Low | Major losses in one or more factors; common in high-variety / low-volume job shops measuring OEE for the first time |
Frequently asked questions
What is a good OEE score?
The widely cited world-class OEE benchmark is 85%, per the OEE Foundation and Seiichi Nakajima's original research. Most manufacturers measuring OEE for the first time score 35–65%. A score of 70–85% is considered good. Context matters: a 75% OEE in a high-mix job shop with frequent changeovers may be excellent, while the same score in high-volume repetitive production leaves significant room for improvement.
What is the difference between planned and unplanned downtime in OEE?
Planned downtime — scheduled breaks, planned maintenance windows, shift changeovers, and meal breaks — is excluded from the OEE calculation. It reduces the denominator (planned production time) and is not treated as a loss. Unplanned downtime — equipment breakdowns, material shortages, unexpected stoppages, and unscheduled maintenance — is captured in the Availability factor and reduces OEE. The distinction is important: only time that could have been producing but was not counts as an OEE loss.
What are the Six Big Losses?
The Six Big Losses framework (Nakajima, 1988) maps each category of loss to an OEE factor:
- Availability losses: (1) Equipment failures — breakdowns requiring unplanned maintenance. (2) Setup and adjustment — changeover time exceeding the standard.
- Performance losses: (3) Idling and minor stoppages — brief pauses under a few minutes (jamming, sensor trips, material feed issues). (4) Reduced speed — running below the design cycle rate.
- Quality losses: (5) Process defects — scrap and rework produced during steady-state production. (6) Reduced yield — startup losses and ramp-up scrap after a changeover or breakdown.
Should I calculate OEE per machine, per cell or per shift?
Calculate OEE at the level you can act on. Most manufacturers start with per shift per machine — this is the finest-grained level that relates to operator behaviour and shift supervision. Rollup to week, month, or across machines is useful for trend monitoring. Avoid averaging OEE across machines with very different processes — a 70% average of a 95% grinder and a 45% press hides the fact that one machine needs urgent attention.
Why is OEE sometimes different from machine utilisation?
Machine utilisation (or machine efficiency) typically measures only whether the machine was running — it ignores speed losses and quality losses. OEE is more comprehensive: it measures whether the machine was running (availability), whether it was running at its design speed (performance), and whether what it produced was good (quality). A machine can have 95% utilisation but 60% OEE if it runs slowly and produces 10% scrap.
Sources
- Nakajima, S. (1988). Introduction to Total Productive Maintenance (TPM). Cambridge, MA: Productivity Press. — Origin of the Six Big Losses framework and 85% world-class benchmark.
- OEE Foundation. "What is OEE?" oee.com. Accessed September 2026. — OEE formula and benchmark definitions.
- SEMI E10-0712 Standard. "Specification for Definition and Measurement of Equipment Reliability, Availability, and Maintainability (RAM)." — Industry standard definitions for equipment time states.