OEE Calculator

How to calculate OEE

OEE = availability × performance × quality. Use ratios before converting the final answer to a percentage. This page uses the Vorne OEE calculation method:

• Planned minutes = observation length − time not scheduled for production.
• Run minutes = planned minutes − stops.
• Availability = run minutes ÷ planned minutes.
• Performance = ideal seconds per unit × total units ÷ (run minutes × 60).
• Quality = first-pass good units ÷ total units.

The direct cross-check is OEE = ideal seconds × good units ÷ (planned minutes × 60). The factor breakdown explains why a score changes. A higher overall score can still hide worse quality, so keep the three factors beside it.

Decide what belongs in each time field

Exclude periods when production was not intended. Track changeovers or breakdowns inside the intended production window as stops, even when scheduled in advance. Good count excludes units that need rework. These distinctions follow Vorne’s definitions of OEE factors. Keep your recording convention consistent between runs.

Worked example: a 480-minute shift

This fictional run has 30 minutes with no production scheduled, 90 minutes of tracked stops, a 1.2-second ideal cycle, 15,000 total units and 14,400 first-pass good units. The planned window is 450 minutes and actual run time is 360 minutes.

Availability is 360 ÷ 450 = 80%. At ideal speed, all 15,000 units require 300 minutes, so performance is 300 ÷ 360 = 83.3333…%. Quality is 14,400 ÷ 15,000 = 96%. Multiplying the unrounded factors gives 64% OEE.

The same record splits into 90 stop minutes, 60 speed-loss minutes, 12 quality-loss minutes and 288 productive minutes. Their sum is 450. The 30 excluded minutes stay outside that breakdown. Quality loss here is equivalent ideal production time, not a claim that a particular defect occupied exactly that many clock minutes.

Try changing only good units to 15,000: quality becomes 100% and OEE becomes 66.6667…%, while availability and performance stay unchanged. That is a calculation scenario, not a forecast that every rejected unit can be recovered.

Use the result without hiding missing data

A blank value is not zero. Check missing times, counts and the product’s ideal cycle before calculating. If performance would exceed 100%, the page stops and asks you to reconcile the inputs; it does not silently cap the value. An entire planned window with no runtime and no output can produce 0% OEE, but performance and quality remain N/A. With runtime but no output, performance is 0% and quality is N/A.

This single-run calculator assumes one valid ideal cycle time. Do not average cycle times across different products and treat the result as a verified mixed-product score. It also cannot identify stop reasons, determine a safe machine speed, calculate staffing, or estimate financial savings. OEE uses planned production time; it is not a measure of 24/7 asset utilization.

For a useful comparison, record the same counting point, product, time units and inclusion rules. Save the input record along with the output. Investigate the largest loss using your logs before deciding on an intervention.

If your next question is the cost of holding the resulting stock, use the Inventory Carrying Cost Calculator. For allocating known purchase and shipping costs across goods, use Landed Cost per Unit. Neither tool turns OEE losses into guaranteed cash savings.