Web service systems grow larger with age whenever organizations add new services to existing systems. As is the case with other types of software, very large Web service systems are difficult to understand and maintain and are therefore undesirable. A couple of measures have been proposed in literature that can be used to analyze the size attribute of Web service systems with the goal of aiding designers and managers in the management of such software. However, these measures target only simple to medium-sized services, and are not effective for very large cross-enterprise services. In this paper, we propose some size measures for evaluating the size of Web service systems irrespective of their granularity, thereby providing useful information to business process managers. We have validated the measures theoretically using Briand's measurement framework