OEE Calculator

What is OEE?

Overall Equipment Effectiveness (OEE) measures how much of the planned production time is truly productive: making good parts, as fast as possible, with no stops. It combines three factors:

OEE = Availability × Performance × Quality

Availability = Run Time ÷ Planned Production Time
Performance  = (Ideal Cycle Time × Total Count) ÷ Run Time
Quality      = Good Count ÷ Total Count

Worked example

An 8-hour shift (480 min) has 30 minutes of planned breaks, so planned production time is 450 minutes. The line stops for 45 minutes, leaving 405 minutes of run time. The ideal cycle time is 60 seconds, and the line makes 380 units, of which 19 are rejected.

• Availability = 405 ÷ 450 = 90.0%
• Performance = (60 s × 380) ÷ (405 × 60 s) = 93.8%
• Quality = 361 ÷ 380 = 95.0%
• OEE = 0.900 × 0.938 × 0.950 ≈ 80.2%

The six big losses

OEE factor	Typical losses
Availability	Equipment failures; setups and changeovers
Performance	Idling and minor stops; reduced speed
Quality	Process defects; startup rejects

Tips for accurate OEE

• Use the true ideal cycle time, the fastest the equipment can run sustainably, not the average or standard rate. If performance comes out above 100%, the ideal cycle time is set too slow.
• Be consistent about planned stops. Decide what counts as planned (breaks, planned maintenance) and apply it the same way on every line.
• Count changeovers as downtime so improvement work on setup time shows up in the number.
• Capture data automatically from PLCs or an MES where possible; manual logs usually under-report short stops.
• Track the three factors, not just the total. The breakdown tells you where to focus.