OEE: Overall Equipment Effectiveness

Six Sigma


The OEE is a quantity that allows you to measure the total efficiency of industrial plants. It encompasses three fundamental concepts of manufacturing production: the availability, efficiency and quality rate of a plant. The OEE is expressed in percentage points: a score of 100 means that the plant produces only good components (100% quality), in the shortest possible time (100% performance) and without downtime (100% availability ).

The importance of the OEE

Measuring and monitoring the OEE is a good production practice. Thanks to this index, in fact, it is possible to obtain fundamental information aimed at optimizing the production process. This is the best measure used to identify leaks, implement and improve plant productivity.

OEE = A * E * Q

To obtain the OEE value of your plants, three characteristic concepts must be considered: availability (A), efficiency (E) and quality (Q).

Availability (in English Availabilty) considers planned shutdowns (setup of scheduled maintenance) and unplanned (breakdowns). These shutdown periods are called DOWNTIME. Availability is defined as the ratio between the time the plant is actually working (UPTIME) and the potential time during which the machinery could work (UPTIME - DOWNTIME).


A score of 100 indicates that the industrial process is always up and running during the planned period.

Efficiency (in English Efficiency) considers slow cycles and short stops. Given the complexity of tracing all the micro-stops of the machinery, the efficiency is calculated deductively and represents the relationship between the real cadence of the plant and the theoretical one.

E = Number of pieces actually produced / Number of pieces theoretically to be produced

A score of 100 corresponds to the best execution of the production process in terms of time.

The rate of quality (in English Quality) considers the components produced by a plant and their percentage of rejection or re-work. The value of the quality rate is obtained from the ratio between the pieces made and compliant with the product specifications, and the total number of pieces actually produced in a specific time interval.

Q (t) = Number of compliant pieces / Number of pieces actually made

A score of 100 indicates the total absence of defects, i.e. an optimal total production without any scrap.