What OEE is
OEE (Overall Equipment Effectiveness) is the standard metric for measuring how productively a machine or line is being used relative to its full theoretical potential. It's the most common way to quantify the machine-related wastes in a process.
The 3 factors in the calculation
OEE is the product of three sub-metrics: OEE = Availability × Performance × Quality
Availability
Actual run time divided by planned production time. Drops with unplanned stops, changeovers, and corrective maintenance.
Performance
Actual production speed divided by the maximum theoretical speed. Drops with minor stops and running below rated capacity.
Quality
Good parts divided by total parts produced. Drops with scrap and rework.
A full worked example
Consider an 8-hour shift (480 minutes), with 30 minutes of planned downtime (lunch), leaving 450 minutes available. The line was down 45 minutes for unplanned failures, leaving 405 minutes of run time. Theoretical capacity is 2 parts/minute, but the line actually ran at 1.8 parts/minute. Out of 729 parts produced, 20 were scrapped.
- Availability = 405 / 450 = 90%
- Performance = (729 parts ÷ 405 min) ÷ 2 parts/min = 1.8 ÷ 2 = 90%
- Quality = (729 − 20) / 729 = 97.3%
- OEE = 0.90 × 0.90 × 0.973 ≈ 78.8%
The 6 big losses OEE measures
OEE ties directly to six loss categories: breakdowns and setup/adjustment (availability); minor stops and reduced speed (performance); process defects and start-up losses (quality).
What isn't measured isn't managed — and OEE is the most direct way to put a number on machine-level waste.
What counts as a good OEE
An OEE of 85% is generally considered world-class for discrete manufacturing. Most plants run between 40% and 60% without a structured improvement program. Before chasing 85%, measure current OEE by line and prioritize the largest of the three losses — availability is usually cheaper to fix than performance or quality.
Want the full OEE calculation walkthrough?
Download the "OEE Calculation in Practice" e-book, with a ready-to-use spreadsheet.
Download the e-book
About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.