OEE Definition #1:

At it’s simplist OEE (Overall Equipment Effectiveness) can be defined as the ratio between actual good output and theoretical good output. Click Here to see a worked example of how to calculate your OEE.
 

 OEE % = Actual Good Units / Theoretical Good Units %

OEE Definition #2:

Fundamentally, OEE (Overall Equipment Effectiveness) is a performance metric compiled from three data sources of the machine (or Process) being measured. The three data sources are Availability, Performance and Quality. Availability, Performance and Quality are all defined below.
 

 OEE % = Availability X Performance X Quality %

Availability Definition for calulating OEE Metric:

Availability is defined as the ratio between the available time (uptime) and the scheduled production time. An Availability of 80% implies that the equipment/process was actively producing product for 80% of the scheduled production time and for the remaining for 20% of scheduled production time the equipment/process was not available to produce (i.e. downtime losses).
 

 Availability % = Uptime / Scheduled Production Time %

Performance Definition for calculating OEE Metric:

Performance is defined as the ratio between the theoretical production time for the total product produced during available time (uptime) and the available time (uptime). A Performance of 90% implies a Speed Loss of 10% (e.g. due to equipment speed being turned down, gaps in product feeding to equipment/process). 
 

 Performance % = Theoretical Production Time for throughput / Available Time %

Quality Definition for calculating OEE Metric:

Quality is defined as the ratio between the good units produced and the throughput. A Quality score of 95% implies a Yield Loss of 5% due to scrapping and/or reworking of product (this reworking consumes capacity in the equipment/process). 

 Quality % = Good Units Produces / Throughput %