Overall Equipment Effectiveness is the measure of a machines overall performance calculated from the effects of what are identified as the 6 Big Losses. They are;

1. Breakdown losses
2. Setup and adjustment losses
3. Idling and minor stoppage losses
4. Reduced speed losses
5. Quality defects and rework
6. Startup losses ( reduced output between starting the machine and stable output)

These losses can be divided into three groups;

1. Availability (Breakdowns & Setup and adjustments)
2. Perfomance Rate (Idling & minor stoppages)
3. Quality Rate (Defects & Start up losses)

To determine each group, the caculations are;

Availability = loading time - down time   =  operation time
               ------------------------      --------------
                    loading time              loading time

Loading time is the available time each day or shift minus the planned downtime, eg. meetings, breaks etc.

Down time is the time lost during the loading time on activies such as change overs, breakdowns, tool changes etc.