OEE Calculator
Overall Equipment Effectiveness from availability, performance and quality
Inputs
Availability
87.5%
Performance
83.3%
Quality
95.7%
OEE
69.8%
Typical range (60-85%)
How it's calculated
Availability
Run time ÷ planned time
Performance
Ideal cycle × units ÷ run time
Quality
Good units ÷ total units
OEE
Availability × Performance × Quality
OEE is the product of three factors:
Availability = run time ÷ planned time, where run time = planned time − downtime.
Performance = (ideal cycle time × total units) ÷ run time.
Quality = good units ÷ total units.
OEE = Availability × Performance × Quality. A world-class benchmark is around 85%.
How to calculate OEE: a worked example
Take one eight-hour shift on a production line, using the same figures the calculator opens with. Planned production time is 480 minutes and the line was down for 60 of them. Its ideal cycle time is 30 seconds a unit, and it made 700 units, of which 670 were good first time.
| Step | Calculation | Result |
|---|---|---|
| Run time | 480 min − 60 min | 420 min |
| Availability | 420 ÷ 480 | 87.5% |
| Performance | (30 s × 700 units) ÷ (420 min × 60 s) | 83.3% |
| Quality | 670 ÷ 700 | 95.7% |
| OEE | 87.5% × 83.3% × 95.7% | 69.8% |
The hour of downtime is the obvious loss, but speed is the bigger one here. Performance gives away almost 17 points, availability 12.5.
The OEE formula, and a quicker check
OEE multiplies three ratios, each of which isolates a different kind of loss. Written out, OEE = Availability × Performance × Quality. Between them they cover the six big losses of total productive maintenance, namely breakdowns, set-up and adjustment, small stops, reduced speed, start-up rejects and production rejects.
Because run time cancels out, the same number comes from a shorter formula, OEE = (good units × ideal cycle time) ÷ planned production time. For the shift above that is (670 × 30 s) ÷ (480 × 60 s), which is 69.8%. It is a handy check on a spreadsheet, though on its own it hides which loss is responsible.
| Factor | Formula | Losses it captures |
|---|---|---|
| Availability | Run time ÷ planned production time | Breakdowns, changeovers and set-ups, waiting on material or operators |
| Performance | (Ideal cycle time × total units) ÷ run time | Minor stops, idling and running below ideal speed |
| Quality | Good units ÷ total units | Scrap, rework and start-up rejects |
What a good OEE score looks like
The figure quoted everywhere is 85 per cent as world class, a benchmark from the total productive maintenance literature. Plenty of lines run nearer 60 per cent, and a first honest measurement often comes in lower than people expect.
Treat the benchmark as a direction rather than a target. OEE depends on how ideal cycle time and planned time are defined, so comparisons between sites only hold when the definitions match, and ISO 22400-2 is a useful reference for pinning them down. The most reliable comparison is a line against its own trend, ideally measured from control system data rather than shift sheets, which is what real-time production analytics makes routine.
On continuous process plants and mining circuits, where output is tonnes per hour rather than units, OEE is often supplemented or replaced by availability and utilisation measures built on the same logic.
Mistakes that distort OEE
- An ideal cycle time that is not ideal. An average or comfortable rate hides speed losses, and a nameplate figure the equipment has never achieved inflates them. Use the fastest rate the line can sustain, and keep it fixed.
- Counting reworked units as good. Quality is first-pass yield, so anything that needed a second attempt is a loss.
- Moving planned time around. Decide once whether breaks, planned maintenance and no-demand periods sit inside planned production time, then apply the rule the same way every shift.
- Averaging OEE across machines. A simple average of percentages misweights short and long runs. Sum the underlying times and counts first, then calculate.
- Accepting performance over 100 per cent. That is always a data problem, usually the ideal cycle time or the unit count, never a line beating its limit.
- Chasing the headline. The value is in which factor moved. A number that went up tells you nothing about what to fix next.
Why it matters
OEE rolls three different losses into one number you can actually track. Most plants run well under their nameplate capacity, but the reasons hide in different places. The asset sits idle, or it runs slow, or it makes product that has to be redone. One figure drags all of that into the light, and it's usually output you're already paying for.
The value is in the split. A plant sitting at 60% with good availability but weak performance has a different problem to one losing the same output to breakdowns or scrap. Fixing the first means chasing minor stops and speed losses. Fixing the second means reliability or quality work. Knowing which one you're looking at tells maintenance, operations and process teams where to push, and gives you a steady baseline to measure against once you start.
Common questions
What is the formula for OEE?
OEE = Availability × Performance × Quality. Availability is run time divided by planned production time, performance is ideal cycle time multiplied by total units and divided by run time, and quality is good units divided by total units. The same result comes from good units multiplied by ideal cycle time, divided by planned production time.
What is a good OEE score?
85 per cent is the widely quoted world-class benchmark, and many lines run nearer 60 per cent. Because OEE depends on how ideal cycle time and planned time are defined, a line's own trend is a more reliable guide than a comparison with another site.
Can OEE be over 100 per cent?
No. A result over 100 per cent means an input is wrong, most often an ideal cycle time slower than the line can really run, or a unit count that covers more than the period being measured.
What is the difference between OEE and TEEP?
OEE measures effectiveness during planned production time. TEEP, total effective equipment performance, measures it against all calendar time, so it multiplies OEE by utilisation, the share of calendar time planned for production. TEEP shows how much capacity sits unused in unscheduled time.
Is OEE the same as availability?
No. Availability is one of the three factors inside OEE. A line can be available 95 per cent of the time and still have a low OEE if it runs slowly or makes scrap.
Related reading
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