OEE is 78.6%—do I need a second line or better OEE?
Model throughput first. At 78.6% on 480 planned minutes you may recover 10%+ capacity from micro-stops before capex.
ZBI Business Control Library
OEE
OEE: plain-English definition, formula, worked example, how to interpret the result, peer-based benchmark guidance, common mistakes, and management actions in the ZBI Business Control Library.
What is OEE?
Overall Equipment Effectiveness rolls availability, performance, and quality into one score for a line or machine. Availability: did it run when scheduled? Performance: did it hit standard rate? Quality: good units first time? A food packaging filler at 92.1% availability, 88% performance, and 97% quality gives OEE ≈ 78.6%. I put OEE on the constraint because plant-wide averages lie—a bottleneck at 55% caps throughput no matter how well other lines run.
Why OEE matters
Capacity and margin hide in OEE gaps. A constraint line at 65% OEE means you buy extra shifts or defer orders—labour and overtime that 78.6% OEE could have avoided. When OEE drops five points for a month, treat it like a financial variance: name the loss bucket, assign an owner, set a date. Ignore it and customers see late deliveries while you quote eight-week lead times you could shorten with better changeover discipline. Maintenance sees rising breakdown hours; finance sees unit cost spike from under-absorbed fixed overhead on the same asset base.
Formula and variables
OEE % = Availability × Performance × Quality
Availability = Run Time ÷ Planned Production Time.
Performance = (Ideal Cycle Time × Total Count) ÷ Run Time.
Quality = Good Count ÷ Total Count.
Excel: =B2*B3*B4*100 when factors are decimals.
Real business example
Dalmatia Foods d.o.o., a EUR 6M processor in Split, runs the filler line Tuesday: 480 planned minutes, 38 lost to breakdowns and changeovers → run time 442; availability 0.921. Ideal cycle 0.8 sec/unit; total count 29,170 → performance 0.88. Good units 28,295 → quality 0.970. OEE = 0.921 × 0.88 × 0.970 ≈ 78.6%. Weekly review compares to internal best shift 84% and targets micro-stop reduction before capex for a second line.
How to interpret the result
Measure OEE on the constraint first; everything else is secondary.
- Availability losses from planned changeovers may be acceptable if batch policy requires them.
- Performance above 100% means ideal cycle times are stale—not superhuman operators.
- Quality losses at the end of the line often trace to earlier process drift.
- Plant average OEE can hide a bottleneck at 55% while the board sees 72%.
Benchmark context
World-class discrete manufacturing often cites 85% OEE on constraints; many plants start in the 60s. Benchmark against your best shift and best line first, then against similar process types in industry studies—not a pharmaceutical line if you run metal stamping. Sustained +3 points year-on-year beats a one-week hero number after a kaizen blitz.
Red flags
- OEE below 70% on the constraint for four consecutive weeks—late orders and overtime follow.
- Performance factor above 1.0—standards outdated; you are underinvesting in realistic planning.
- Availability losses rising while PM compliance looks fine—breakdown pattern, not random noise.
- Quality factor drops below 95% on one SKU family—scrap cost and customer complaints ahead.
- OEE flat but schedule adherence falling—building WIP to hit units, not fixing losses.
Common mistakes
- Reporting plant-wide OEE while the bottleneck runs 15 points lower.
- Excluding changeover from availability without documenting the policy.
- Using ideal cycle times from a 2019 study that no longer matches the product mix.
- Counting rework as good units in the quality factor.
- Reviewing OEE monthly without shift-level loss categories.
What should management do next?
- Display live OEE and top loss reason at the constraint work centre each shift.
- Run daily 15-minute loss analysis with production, maintenance, and planning.
- Reset ideal cycle times annually from engineering time studies on current mix.
- Tie PM work orders to recurring availability loss codes from the last 90 days.
- Track OEE eight weeks after any kaizen or automation project before closing the action.
Related calculators
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FAQ
Maintenance wants to exclude all changeovers from availability—is that allowed?
Only if you define planned non-production separately and report both numbers. Hiding changeovers inflates OEE.
Which line do I measure first with limited MES budget?
The constraint—the line that caps customer delivery. Non-constraint OEE is diagnostic, not priority.
Can I tie operator bonus to OEE?
Yes on assigned lines, with quality factor as a gate. Bonus on speed alone invites rework.
OEE improved but unit cost did not—why?
Check volume absorption and material scrap outside the OEE quality count. OEE is equipment effectiveness, not full cost.
Summary
OEE measures how effectively equipment produces good units at standard rate when scheduled. Measure it on constraints, classify losses honestly, and improve through daily habits.
Reviewed by ZBI Business Control Library · Last updated 2026-06-15