Lean teams use OEE to find and rank equipment losses. Breaking the score into its three factors points to downtime, slow cycles or defects. It works best as a tool for improvement on one asset, not as a ranking between plants.
Where it comes from
OEE emerged from Total Productive Maintenance in Japan. Seiichi Nakajima popularized it as a way to measure the six big losses.
At a glance
Where the planned time goes
Swipe sideways to see the whole diagram.
How to apply Overall Equipment Effectiveness
- 1
Define planned production time
Start with shift time and remove planned breaks and periods with no scheduled production. This is the base for all three factors.
- 2
Calculate availability
Divide run time by planned production time. Run time is planned time minus unplanned stops and changeovers.
- 3
Calculate performance
Multiply ideal cycle time by total count, then divide by run time. Use the true design or best demonstrated speed, not a padded standard.
- 4
Calculate quality
Divide good count by total count. Count only parts that are good the first time, without rework.
- 5
Multiply and analyze the losses
OEE equals availability times performance times quality. Map the gaps to the six big losses and pick the largest one to attack.
- 6
Track by shift and act
Review OEE and its loss reasons in daily meetings. Assign countermeasures and watch whether the targeted factor improves.
Worked example
A filling line has 420 minutes planned, with 42 minutes of stops, giving 90 percent availability. It makes 3,240 bottles at an ideal rate of 10 per minute, for about 86 percent performance. With 3,180 good bottles, quality is about 98 percent, so OEE is roughly 76 percent.
Common mistakes
- Using a slow or padded ideal cycle time, which inflates performance and hides speed losses.
- Comparing OEE across different machines or plants as if it were a fair league table.
- Reporting only the headline number without the loss reasons needed to act.
When Overall Equipment Effectiveness is not the right tool
OEE is a measure of one asset or line, not a target to compare plants. Different definitions of planned time make cross-site comparisons misleading.
Use it to find and rank losses on your own equipment, then track the trend against your own baseline.
OEE meaning
OEE stands for overall equipment effectiveness. It shows how much of the planned production time a machine spends making good parts at full speed.
Seiichi Nakajima set out OEE as part of total productive maintenance in Japan. The TPM page covers that wider system.
OEE formula and calculation
The OEE formula is availability multiplied by performance multiplied by quality. Each factor is a percentage of the time or parts that were possible.
Availability is run time divided by planned production time. Performance is ideal cycle time multiplied by total count, divided by run time. Quality is good count divided by total count.
A shortcut gives the same result: good count multiplied by ideal cycle time, divided by planned production time. The OEE calculator does the arithmetic for you.
OEE example
Say a shift has 480 minutes of planned production time and the machine stops for 48 minutes. Run time is 432 minutes, so availability is 90%.
The ideal cycle time is one minute per part, and the machine makes 380 parts. Performance is 380 divided by 432, or about 88%.
Of the 380 parts, 361 are good, so quality is 95%. OEE is 90% × 88% × 95%, or about 75%. The shortcut agrees: 361 good minutes out of 480.
A shortcut formula
OEE can also be calculated as good count times ideal cycle time, divided by planned production time. It gives the same result as multiplying the three factors.
The OEE calculator shows both the factors and the losses behind them.
| Factor | Losses it captures |
|---|---|
| Availability | Failures; setups and adjustments |
| Performance | Minor stoppages; reduced speed |
| Quality | Scrap; rework |