CNC OEE Calculator and Formula
Plug in one shift for one machine and see availability, performance, quality, and OEE instantly — then learn how to calculate it correctly for a high-mix CNC shop.
CNC OEE calculator
Enter one shift (or one week) for a single machine. Everything runs in your browser — nothing is sent anywhere.
OEE — Overall Equipment Effectiveness — is the share of planned production time that turns into good parts at full speed. The calculator above does the arithmetic. The rest of this page explains each input, walks through real CNC examples, and covers the mistakes that make OEE look better than it is.
OEE = Availability × Performance × Quality. The formula takes a minute to learn. Getting honest inputs — real stop time and a real ideal cycle — is the actual work.
The OEE formula, step by step
1. Availability
Availability = Run time ÷ Planned production time
- *Planned production time* is the time you intended the machine to make parts — usually the shift length minus planned breaks and any time you deliberately did not schedule.
- *Run time* is planned production time minus every stop: breakdowns, alarms, waiting for material or programs, inspections, and (in most job shops) setups.
Example: 480 planned minutes, 72 minutes of stops. Run time = 408 minutes. Availability = 408 ÷ 480 = 85.0%.
2. Performance
Performance = (Ideal cycle time × Total parts) ÷ Run time
This compares how many parts you made with how many the machine could have made in the run time at its ideal cycle.
Example: ideal cycle 90 seconds, 230 parts made. Ideal time for those parts = 230 × 90 = 20,700 seconds = 345 minutes. Performance = 345 ÷ 408 = 84.6%.
3. Quality
Quality = Good parts ÷ Total parts
Example: 221 good parts out of 230. Quality = 96.1%.
4. OEE
OEE = 0.850 × 0.846 × 0.961 = 69.1%
Put differently: of 480 planned minutes, about 332 produced good parts at full speed. The other ~148 minutes were lost to stops (72), slow cycles (about 63), and rejects (about 13). That breakdown matters more than the headline number — it tells you where to look first.
Worked example: a high-mix job shop week
Here is a vertical machining center across one week of two shifts.
| Input | Value |
|---|---|
| Planned production time | 5 days × 2 shifts × 450 min = 4,500 min |
| Stops (incl. 11 setups) | 1,620 min |
| Run time | 2,880 min |
| Parts produced (mixed jobs, weighted ideal time) | Ideal time total 2,300 min |
| Good parts | 98.5% |
- Availability = 2,880 ÷ 4,500 = 64.0%
- Performance = 2,300 ÷ 2,880 = 79.9%
- Quality = 98.5%
- OEE = 50.4%
For mixed jobs, sum ideal time across every part produced (ideal cycle × quantity for each job) instead of using one cycle time. This is exactly the kind of bookkeeping monitoring software does for you.
The lesson from this example is typical: availability is the biggest loss. Eleven setups and the waits around them cost more than every slow cycle combined. Setup reduction, staging tools and material ahead of time, and getting first-article approval faster would move this machine more than any program optimization.
OEE benchmarks — use with care
| OEE | What it usually means |
|---|---|
| Below 40% | Typical first measurement in many high-mix shops once short stops are counted. Large, often easy, availability gains. |
| 40–60% | Common for job shops with frequent changeovers. |
| 60–75% | Solid for high-mix work. Repeat-part cells often land here. |
| 75–85% | Strong. Usually dedicated or long-run production. |
| 85%+ | The classic "world-class" figure from high-volume lines. Rare in true job shops. |
The 85% benchmark was built for long production runs of one part. Comparing a 200-job-a-month shop against it is discouraging and misleading. Compare each machine with its own baseline and against similar machines doing similar work.
Seven mistakes that inflate (or wreck) OEE
- Excluding setups without saying so. OEE jumps, nothing improved. Pick a definition and write it down.
- Using quoted cycle times as ideal. Quotes include padding, so performance looks great. Use the best proven cycle.
- Ignoring short stops. Manual logs miss stops under 10–15 minutes, which often add up to the largest loss.
- Changing planned time to match reality. If second shift "wasn't really planned" every time it underperforms, OEE becomes fiction.
- Averaging percentages across machines. Weight by planned time, or a tiny machine skews the shop number.
- Counting reworked parts as good. Quality means first-pass good.
- Reporting OEE without the losses. A single percentage cannot tell you what to fix. Always show availability, performance, and quality — and the top stops.
OEE vs TEEP vs utilization
| Metric | Denominator | Question it answers |
|---|---|---|
| OEE | Planned production time | How effective were we when we planned to run? |
| TEEP | All calendar time (24/7) | How much of the machine's total possible time became good parts? |
| Utilization | Calendar or scheduled time | How much of the time was the machine running at all? |
TEEP and utilization are the numbers to watch before buying another machine — unscheduled nights and weekends are capacity too. Calculate yours with the machine utilization calculator.
Calculating OEE automatically
The calculator is useful for one machine and one shift. Doing it for every machine every day by hand is not realistic, and the stop times will be wrong anyway. CNC monitoring software reads run state and part counts from the machine and calculates OEE continuously. FEAI Machine Monitor's OEE uses MTConnect data from supported machines, lets you set planned time and an ideal cycle per machine, and shows the stops behind every lost point.
Next steps
- Run the calculator with last week's numbers for your bottleneck machine.
- Write down your definitions: planned time, planned stops, and how you set ideal cycles.
- Find the biggest loss — usually availability — and read CNC Downtime Tracking to start shrinking it.
- When you are tired of doing it by hand, monitor two machines free.
FAQ
What is the OEE formula?
OEE equals Availability times Performance times Quality. Availability is run time divided by planned production time. Performance is ideal cycle time times total parts divided by run time. Quality is good parts divided by total parts.
What is a good OEE score for CNC machines?
85% is often called world class, but that benchmark comes from high-volume production lines. High-mix CNC job shops commonly measure far lower once all stops are counted. Track your own trend instead of chasing a generic number.
Should setup time count against OEE?
It depends on your definition, but many job shops count setups as availability loss because setup reduction is one of the biggest improvement opportunities. Whatever you choose, keep it consistent.
Why is my OEE over 100%?
Usually the ideal cycle time is set too slow, which pushes performance above 100%. Use the fastest proven cycle for the part.
What is the difference between OEE and TEEP?
OEE measures effectiveness during planned production time. TEEP measures it against all calendar time, so it also exposes unscheduled shifts and weekends.
Can OEE be calculated automatically?
Yes. Monitoring software reads run time and part counts from the machine, so you only configure planned time and ideal cycles.