The Real-time Overall Equipment Effectiveness (OEE) Tool is a proposed automatic performance measurement tool. It is for use in the implementation and operation of a Total Productive Maintenance (TPM) programme. The tool is a Personal Computer based system, integrating the TPM elements of OEE measurement and Employee Involvement, with Supervisory Control and Data Acquisition (SCADA) technology. This provides automatic collection and presentation of machine operation and OEE data to operators on the factory floor, in real-time. In this paper, the motivation and elements of such a tool, and the essential features of one are discussed. Software is presented demonstrating a Real-time OEE tool written for a particular machine. The benefits and possibilities for using this type of tool as part of a TPM implementation methodology are discussed.