Method / assumptions / examples
How this calculation works
The result is deterministic: the same measurements always return the same estimate. Here is the relationship and where real-world results can differ.
Formula
Availability = run time ÷ planned time; Performance = (ideal cycle × total count) ÷ run time; Quality = good count ÷ total count; OEE = A × P × Q
Run time is planned production time minus recorded stop time. Availability exposes stop loss, Performance exposes slower cycles and short stops that remain inside run time, and Quality exposes rejected or reworked output. Multiplying the three factors also gives the equivalent direct relationship OEE = (ideal cycle time × good count) ÷ planned production time. Run time and total count cancel algebraically. That is why changing only stop time while holding output fixed moves loss between Availability and Performance without changing OEE: the same output in less run time implies a faster operating rate.
Worked example
Examples
With 480 planned minutes, 45 stopped minutes, a 1.5-second ideal cycle, 15,000 total units, and 14,550 good units: Availability is 90.6%, Performance is 86.2%, Quality is 97.0%, and OEE is 75.8%. The good output represents 363.8 ideal minutes out of 480 planned minutes.
If the same 15,000 units are reported with more stop time, Availability falls but Performance rises because those units were made in fewer run minutes. OEE stays at 75.8% until planned time, ideal cycle, or good output changes. The factors redistribute the loss rather than count it twice.
Common mistakes
What to check before using the result
- Define the boundary first: one asset or line, one product or documented product mix, and one exact reporting period. Every input must use that same boundary.
- Enter only time the equipment was intended to produce as planned production time. Exclude unscheduled shifts and other schedule loss; decide consistently whether planned breaks belong inside or outside this boundary.
- Classify stops consistently. Longer stops normally reduce Availability, while short stops left inside run time reduce Performance through lower output.
- Use a validated ideal cycle for the selected product and count unit—not the average cycle achieved during the period. For mixed products, calculate segments separately or use a documented weighted method.
- Count first-pass conforming output as good. Rework, scrap, and startup rejects belong in total count but not good count for that first pass.
- If Performance exceeds 100%, check the ideal cycle, time units, product or lane count basis, and stop records before trusting the result.
FAQ
Frequently asked questions
What do Availability, Performance, and Quality mean?
Availability measures how much planned production time remained after recorded stops. Performance compares the ideal time for all output with actual run time. Quality is the first-pass good count divided by total count. Together they separate stop, speed, and reject losses.
Why did changing stop time not change OEE?
If total and good counts stay fixed, more stop time means the same output was produced during fewer run minutes. Availability falls while calculated Performance rises by the offsetting amount. This is expected because OEE also equals ideal cycle time multiplied by good count, divided by planned production time. In real records, stop time and output usually change together.
What is a good OEE score?
There is no universal target that makes unlike assets, products, and reporting rules directly comparable. Establish a consistent baseline for the same process, then investigate which factor and recorded loss category changed.
Should planned breaks be included?
If production was never intended during a break, subtract it before entering planned production time. If your site deliberately includes that break in the production window, record the stopped portion consistently. Document the convention so comparisons use the same boundary.
Why can performance exceed 100%?
The recorded output implies operation faster than the entered ideal rate. Check seconds versus minutes, product-specific ideal cycle, whether count is per lane or across all lanes, and which stops were removed from run time. The calculator reports and flags the value rather than silently clamping it.
Primary references
Sources and standards
- Towards Effective Interface Designs for Collaborative HRI in Manufacturing: Metrics and Measures — National Institute of Standards and Technology
- ISO 22400-1: Manufacturing operations management KPI concepts and terminology — International Organization for Standardization
- Overall Equipment Effectiveness — Lean Enterprise Institute