Free calculator
OEE calculator: free OEE calculation, formula and worked example
Overall equipment effectiveness (OEE) tells you how much of your planned production time made good parts at full speed. The OEE calculation multiplies three factors: Availability (run time over planned time), Performance (ideal output time over run time) and Quality (good count over total count).
Your result
Enter your numbers and press Calculate. The formula and a worked example are below.
| Loss group | Six big losses | Minutes |
|---|---|---|
| Availability | Breakdowns and setups | … |
| Performance | Small stops and slow cycles | … |
| Quality | Startup rejects and production rejects | … |
85% is the figure most often quoted as world class (Nakajima, TPM). Many plants start between 40% and 60%.
OEE = Availability x Performance x QualityNothing you type leaves your browser until you unlock your result. When you do, your numbers and result go to our team with your email, so we can follow up.
The formula
The OEE formula is the product of three factors. Each one is a fraction between 0 and 1. Multiply them and show the result as a percentage.
OEE = Availability x Performance x Quality- Availability
- The share of planned production time the machine actually ran.
- Performance
- How close to its ideal speed the machine ran while it was running.
- Quality
- The share of parts that were good the first time.
Run time
Run time = Planned production time - Stop time- Planned production time
- The minutes the machine was scheduled to produce. Leave out planned breaks, planned maintenance and time with no orders.
- Stop time
- Minutes the machine was stopped inside planned time: breakdowns, setups, changeovers, waiting for material.
Availability
Availability = Run time / Planned production time- Run time
- Planned production time minus stop time, from the formula above.
- Planned production time
- The same scheduled minutes.
Performance
Performance = (Ideal cycle time x Total count) / Run time- Ideal cycle time
- The fastest proven time to make one part, in seconds. Divide by 60 to get minutes before you use it here.
- Total count
- Every part made in the run, good or bad.
- Run time
- The same run time, in minutes.
If Performance comes out above 100%, the ideal cycle time is probably set too slow. Fix the ideal, not the count.
Quality
Quality = Good count / Total count- Good count
- Parts that passed first time, with no rework.
- Total count
- Every part made, the same figure used for Performance.
Loss minutes
The same inputs tell you how many minutes each kind of loss cost you. Minutes are easier to act on than percentages.
Availability loss = Stop time; Performance loss = Run time - (Ideal cycle time x Total count); Quality loss = (Total count - Good count) x Ideal cycle time- Availability loss
- The stop time itself: breakdowns and setups.
- Performance loss
- Run time minus the ideal time for every part made: small stops and slow cycles.
- Quality loss
- Ideal time spent on parts that were rejected: startup rejects and production rejects.
Convert the ideal cycle time to minutes first. Planned time minus the three losses leaves the fully productive minutes.
Worked example
Worked example (illustrative)
Take a green sand moulding line in a foundry near Rajkot. One shift is 480 minutes and the team takes a 30 minute meal break, so planned production time is 450 minutes. During the shift the line stops for 54 minutes: a 36 minute hydraulic breakdown and an 18 minute pattern change. The ideal cycle time is 30 seconds per mould (0.5 minutes). The line makes 660 moulds, and 627 are good.
All numbers are illustrative and the arithmetic is the same as the calculator above.
| Item | Calculation | Result |
|---|---|---|
| Planned production time (input) | 480 - 30 | 450 min |
| Stop time (input) | 36 + 18 | 54 min |
| Ideal cycle time (input) | 30 s / 60 | 0.5 min per mould |
| Total count / good count (input) | 660 / 627 | |
| Run time | 450 - 54 | 396 min |
| Availability | 396 / 450 | 88.0% |
| Performance | (0.5 x 660) / 396 = 330 / 396 | 83.3% |
| Quality | 627 / 660 | 95.0% |
| OEE | 0.880 x 0.8333 x 0.950 | 69.7% |
| Availability loss | Stop time | 54 min |
| Performance loss | 396 - 330 | 66 min |
| Quality loss | (660 - 627) x 0.5 | 16.5 min |
| Fully productive time | 627 x 0.5 | 313.5 min |
OEE is 69.7%. As a check, 313.5 productive minutes out of 450 planned also gives 69.7%, and 54 + 66 + 16.5 + 313.5 adds back to 450. The biggest loss here is Performance at 66 minutes, so small stops and slow cycles are worth a look before more breakdown work.
How to read your result
85% is the figure most often quoted as world class (Nakajima, TPM). Many plants start between 40% and 60%.
Do not stop at the single number. Look at which factor is lowest, then at the loss minutes. Low Availability points at breakdowns, slow repairs and long setups, which your maintenance team and your setup crew own. Low Performance points at small stops, jams and machines running below rated speed. Low Quality points at startup scrap and process rejects.
The most useful comparison is your own machine against itself, week after week, with the same rules for what counts as planned time and stop time. A rise from 55% to 62% on the same rules is real progress. A jump caused by changing the rules is not.
Common mistakes in OEE calculation
Most wrong OEE figures come from the inputs, not the arithmetic. Watch for these.
- Counting planned maintenance as downtime. A scheduled PM is not a stop inside planned production time. Take it out of planned time, or Availability looks worse than it is.
- Leaving meal breaks in planned time. The same rule applies. If nobody planned to produce, it is not planned production time.
- Setting the ideal cycle time too slow. If Performance goes over 100%, the ideal is wrong. Use the design rate or the best rate you have proven.
- Counting reworked parts as good. Quality counts only parts that were right the first time.
- Averaging OEE percentages across machines. Add up the minutes and counts first, then calculate. Otherwise a short run on one machine skews the plant figure.
- Mixing seconds and minutes. Convert the ideal cycle time to minutes before you multiply it by the count.
How MaintenanceIQ helps
You stop rebuilding OEE in a spreadsheet at the end of each shift. In MaintenanceIQ, Availability is derived from the breakdowns your team already logs, and the shift log is picked up from your machine sensors, or entered by the supervisor where a machine has no sensor. See OEE in MaintenanceIQ.
Sources
- Calculate OEE: definitions, formulas and examples (opens in a new tab), OEE.com (Vorne Industries). The Availability, Performance, Quality and run time formulas.
- World class OEE (opens in a new tab), OEE.com (Vorne Industries). The 85% figure and its origin in Seiichi Nakajima's TPM work.
Frequently asked questions
What is a good OEE score?
The figure most often quoted is 85%, from Nakajima's TPM work, and many plants start between 40% and 60%. The best comparison is your own machine against itself over time, with the same rules each time.
Can Performance be over 100%?
Not if the ideal cycle time is right. A Performance figure above 100% usually means the ideal cycle time is set slower than the machine can really run.
Should changeovers count against Availability?
In standard OEE, yes. A changeover inside planned production time is stop time. Some plants report setups separately, which is fine as long as you say so.
Should planned maintenance count as downtime?
No. Planned maintenance is taken out of planned production time, the same as a meal break. Only stops inside planned time count against Availability.
How often should I calculate OEE?
Per shift for each machine is a good start. It is short enough to remember what happened and long enough to smooth out one odd cycle.
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