A solution (300) for metering usage of software products on a data processing system is proposed. In this context, it is often necessary to known a processing power of each computer wherein a generic software product ran (for example, for licensing accounting based on differentiated charging rates). In the proposed solution, the processing power is estimated dynamically on the computer directly. For this purpose, a (single-threaded) benchmark program written in a low-level language is executed (308-322), such as at the startup or periodically. In this way, dividing (324) the measured execution time of the benchmark program by the known number of its instructions it is possible to determine an execution rate of a single microprocessor of the computer. This value multiplied (326) by the detected (306; 332) number of available microprocessors provides an accurate estimate of the processing power of the computer. The desired result is achieved without requiring any knowledge of the physical details of the computer; this is particularly advantageous when the computer consists of a logical guest machine implemented on a physical host machine.