OEE Calculator

What is OEE (Overall Equipment Effectiveness)?

OEE is the standard yardstick for how well a machine or line turns planned production time into good product. It rolls three separate loss buckets, stop losses, speed losses and quality losses, into one percentage, which makes it easy to compare shifts, lines and plants on the same basis.

The OEE Formula

OEE = Availability x Performance x Quality

Each factor is calculated on its own and then multiplied together:

• Availability = Run Time / Planned Production Time, where Run Time is planned time minus all downtime and stops.
• Performance = (Ideal Cycle Time x Total Pieces) / Run Time, with the ideal cycle time converted to the same units as run time.
• Quality = Good Pieces / Total Pieces, where Good Pieces is total pieces minus rejects and rework.

The Three Factors Explained

Availability answers "was the machine running when it was supposed to be?" and drops with breakdowns, changeovers and material waits. Performance answers "when it was running, did it run at full speed?" and drops with minor stops and slow cycles. Quality answers "of what it made, how much was sellable?" and drops with scrap and rework. Because the three are multiplied, a weak factor pulls the whole score down fast, which is exactly what points you at the biggest loss.

The 85% World-Class Benchmark

A widely used rule of thumb puts world-class OEE at about 85% (roughly 90% Availability, 95% Performance and 99% Quality). Many plants run closer to 60%, and 40% is common for lines that have only just started measuring. Treat these as reference points, not hard targets, and focus on moving your own trend line up.

Worked Example

Take a shift with 480 minutes of planned production time and 60 minutes of downtime, so Run Time is 420 minutes. Availability is 420 / 480 = 87.5%. With an ideal cycle time of 60 seconds (1 minute) per piece and 400 pieces made, Performance is (1 x 400) / 420 = 95.2%. With 8 rejects, Good Pieces is 392, so Quality is 392 / 400 = 98.0%. Multiplying the three, OEE = 0.875 x 0.952 x 0.980 = 81.7%. That single number tells you the line was productive for about four-fifths of its planned time.