How to calculate OEE: availability × performance × quality
OEE (overall equipment effectiveness) multiplies three ratios: availability (run time ÷ planned production time), performance (ideal cycle time × total parts ÷ run time) and quality (good parts ÷ total parts). A machine planned for 420 minutes that runs 360, makes 300 parts with a 1-minute ideal cycle and has 291 good parts scores 85.7% × 83.3% × 97% ≈ 69%.
Guilherme Rodrigues ItinoseUpdated 2 min read
Key takeaways
- OEE = availability × performance × quality.
- Use the ideal cycle time, not the average or the quoted one.
- Planned stops (no orders, planned breaks) are outside the calculation; unplanned ones count.
- Compare the three factors to know where the losses are.
- Automatic data from the machine beats end-of-shift paperwork.
OEE is the most used machine effectiveness indicator because it fits on one line and still shows where time is lost.
The formula
OEE = Availability × Performance × Quality
| Factor | Formula | Loss it shows |
|---|---|---|
| Availability | Run time ÷ Planned production time | Breakdowns, setups, waiting |
| Performance | (Ideal cycle × Total parts) ÷ Run time | Slow cycles, micro-stops |
| Quality | Good parts ÷ Total parts | Scrap and rework |
Worked example
- Planned production time: 420 min (8 h shift minus 60 min planned breaks)
- Unplanned stops: 60 min → run time 360 min
- Ideal cycle time: 1.0 min/part, total parts: 300, good parts: 291
Availability = 360 / 420 = 85.7% Performance = (1.0 × 300) / 360 = 83.3% Quality = 291 / 300 = 97.0% OEE = 0.857 × 0.833 × 0.970 ≈ 69.3%
Common mistakes
- Using the average cycle instead of the ideal one, which hides speed losses.
- Excluding setups from downtime because they are “normal”.
- Collecting stops on paper at the end of the shift, when nobody remembers the reasons.
ISO 22400-2 defines OEE and related manufacturing KPIs if you need a formal reference.
CNC Pulse reads FANUC controllers and calculates OEE automatically, with the loss Pareto. See also our automation work.
When to outsource this
- You want OEE without operators filling out forms
- Your OEE numbers are not trusted by the shop floor
When not to
- You do not yet record stops at all; start with simple stop tracking
FAQ
What is a good OEE?
Around 85% is often cited as world class for discrete manufacturing; many plants start between 40% and 60%. Track your own trend first.
Should setup time count as downtime?
Yes, setup is an availability loss. Separating it in the Pareto shows whether setup reduction is worth it.
Can performance be above 100%?
Only if the ideal cycle time is wrong. Fix the reference instead of accepting over 100%.
Where does the data come from?
Ideally from the machine controller: run state, part count and cycle times, plus scrap recorded by quality.
Sources
Send us one drawing
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