Over the past century, open pit mines have steadily increased their production rate by using larger equipments which require intensive capital investment. Low commodity prices have forced companies to decrease their unit cost by improving productivity. One way to improve productivity is to utilize equipment as effectively as possible. Therefore, the accurate estimation of equipment effectiveness is very important so that it can be increased. Overall Equipment Effectiveness (OEE) is a well-known measurement method, which combines availability, performance and quality, for the evaluation of equipment effectiveness in manufacturing industry. However, there isn't any study in literature about how to use this metric for mining equipments such as shovel, truck, drilling machine etc. This paper will discuss the application of OEE to measure effectiveness of mining equipment. It identifies causes of time losses for shovel and truck operations and introduces procedure to record time losses. The procedure to estimate OEE of shovels and trucks has also been presented via numerical example.