OEE: separate downtime, speed losses and rejected units
Calculate availability, performance and quality on one time basis, and understand why OEE differs from capacity utilization.
Method
Overall equipment effectiveness combines three different questions: how much scheduled time the equipment ran, how quickly it produced during that run, and how many units passed without rework. Availability is run time divided by planned production time. Performance compares ideal production time with actual run time. Quality is good units divided by all produced units. Multiply the three fractions, then express the product as a percentage.
Choose one period and one product or a defensible common ideal cycle time. Planned production time excludes periods when production was not scheduled; it must not quietly exclude a breakdown that happened during scheduled production. Good units are those meeting requirements on the first pass. A final shipment count that includes repaired units would answer a different question and can hide quality losses.
Multiply fractions, not percentage integers.
View data
- Availability
- 87.5 % 420 / 480
- Performance
- 95.238095 % 24000 / 25200
- Quality
- 95 % 11400 / 12000
- OEE
- 79.166667 % 0.875 × 0.95238095… × 0.95
Worked example
Consider 480 planned minutes, 420 running minutes, an ideal cycle of 2 seconds, 12000 total units and 11400 good units. Availability is 87.5%, performance about 95.24%, and quality 95%. OEE is about 79.17%. Do not average the three percentages or multiply their displayed whole-number values. Convert each percentage to its fraction and keep precision until the final display.
Enter those five values in the OEE calculator. Independently check that ideal time for the good units is 2 × 11400 = 22800 seconds, or 380 minutes. Dividing 380 by 480 gives the same OEE. This shorter check verifies the combined result; retaining the three factors still helps distinguish lost scheduled time, slow running and first-pass defects.
A = 420 ÷ 480 = 0.875
P = (2 × 12000) ÷ (420 × 60) = 0.95238095…
Q = 11400 ÷ 12000 = 0.95
OEE = A × P × Q = 0.79166666… ≈ 79.17%
Illustrative values, using the method described above.
View data
- Ideal time for good units
- 2 × 11400 / 60 = 380 min
- Planned production time
- 480 min
- Ratio
- 380 / 480 ≈ 79.17%
Checks and limits
OEE is not profit, calendar utilization or a promise of safe capacity. Two processes with the same OEE can have very different loss patterns. A performance result above 100% usually calls for checking the ideal cycle, units and reporting period; the calculator rejects that inconsistency. Use measurements and a consistent definition over time before comparing lines, and investigate the losses rather than treating an illustrative percentage as a universal target.
Related calculators
Source: Vorne — OEE calculation