Guide · OEE
How to Calculate OEE (and Actually Improve It)
ngaide · 28 June 2026
OEE — Overall Equipment Effectiveness (TRS in many plants) — is the single number that tells you how much of your planned production time is truly productive. It is the product of three rates, and its power is that it separates three different problems you fix in completely different ways.
The formula: Availability × Performance × Quality
OEE = Availability × Performance × Quality
- Availability = Run Time ÷ Planned Production Time — captures time lost to stops (breakdowns and changeovers).
- Performance = (Ideal Cycle Time × Total Count) ÷ Run Time — captures speed losses: minor stops and slow cycles.
- Quality = Good Count ÷ Total Count — captures units you made but can’t sell.
Planned Production Time is shift time minus planned shutdowns (breaks, no demand): you only hold the line accountable for time you intended to run.
A worked example
The same OEE can hide very different lines. A 70% built from (86% × 83% × 98%) has a speed problem; a 70% built from (95% × 90% × 82%) has a quality problem. The breakdown is the whole point.
The six big losses
Each factor maps to two classic loss buckets:
- Availability: unplanned stops (breakdowns) and planned stops (setup & changeover).
- Performance: small stops (idling, minor stops) and slow cycles (reduced speed).
- Quality: production rejects (steady-state defects) and startup rejects (warm-up scrap).
What counts as a good OEE?
The widely cited world-class benchmark is 85% — roughly 90% availability × 95% performance × 99.9% quality. It is a useful target, not a law: the right goal depends on your process and your market. Treat the benchmark as a direction and your own trend as the real scoreboard.
From a number to an action
OEE only helps if it changes what you do next. Track it over time, find which of the three factors is dragging, and attack the matching losses. ngaide’s OEE module computes all three factors and the six big losses from your data, flags the limiting factor, and the assistant turns it into a prioritized action plan you can export.