How do you calculate OEE?
Short answer
OEE is availability × performance × quality. Availability is run time divided by planned production time. Performance is total count times ideal cycle time divided by run time. Quality is good count divided by total count. Multiply the three, or use good count × ideal cycle time ÷ planned production time.
OEE, or overall equipment effectiveness, is the share of planned production time that produced good units at the ideal rate. It is built from three ratios. Each one uses figures a line usually records: planned time, stop time, unit counts and the ideal cycle time.
What inputs do I need to calculate OEE?
- Planned production time: scheduled time in minutes, after breaks and planned maintenance are removed.
- Run time: planned production time minus unplanned stops, such as breakdowns and material shortages.
- Ideal cycle time: the fastest time to make one unit of the product that ran, in seconds.
- Total count and good count: all units made, and the units that passed quality without rework.
What are the three OEE factors and how are they calculated?
- Availability = run time / planned production time
- Performance = (ideal cycle time × total count) / (run time × 60)
- Quality = good count / total count
The 60 converts the ideal cycle from seconds to minutes. OEE is the product of the three factors.
What does a worked OEE calculation for a packaging line look like?
A packaging line runs a 480-minute shift with 60 minutes of scheduled breaks, so planned production time is 420 minutes. It has 36 minutes of unplanned stops, which leaves 384 minutes of run time. The ideal cycle is 0.5 seconds per carton. The line packs 36,000 cartons, and 34,920 of them pass inspection.
| Factor | Calculation | Result |
|---|---|---|
| Availability | 384 / 420 | 91.4% |
| Performance | (0.5 × 36,000) / (384 × 60) | 78.1% |
| Quality | 34,920 / 36,000 | 97.0% |
| OEE | 0.9143 × 0.7813 × 0.9700 | 69.3% |
The same answer comes from one formula: 34,920 × 0.5 / (420 × 60), which is 69.3%. Run time and total count cancel, so the two methods always agree.
The largest loss here is performance. While running, the line produced at 78.1% of its ideal rate. The 36,000 cartons at 0.5 seconds each are 300 minutes of ideal output, set against 384 minutes of run time.
What mistakes do people make when calculating OEE?
- Treating planned breaks as downtime. They come out of planned production time before availability is calculated. Leaving them in lowers availability without any change on the line.
- Using the wrong product's ideal cycle. Performance should use the ideal rate of the product that ran, not the fastest product on the line.
- Reading performance above 100%. It means the ideal cycle is set too long, or the counts and run time cover different periods.
- Averaging shift percentages. Add the minutes and counts across shifts, then calculate the factors from the totals.
How do I set up an OEE calculation in a spreadsheet?
The OEE calculator is the Sheet Reserve template for this calculation. To build the same check yourself, put one shift per row. Enter planned production time in column A, unplanned stops in B, ideal cycle time in C (seconds), total count in D and good count in E. Then, in row 2:
- Run time, F2:
=A2-B2 - Availability, G2:
=F2/A2 - Performance, H2:
=D2*C2/60/F2 - Quality, I2:
=E2/D2 - OEE, J2:
=G2*H2*I2
With the packaging figures these return 384, 91.4%, 78.1%, 97.0% and 69.3%. For several shifts, sum the minutes and counts with SUMIFS and divide the totals, not the percentages.
For the full method, including a second shift, the six big losses and the 85% benchmark, read how to calculate OEE: availability, performance and quality.