This paper describes a laboratory experiment which evaluates OO-Method Function Points for the Web. OOmFPWeb measures the functional size of Web applications using conceptual models that are developed with Object-Oriented Web Solutions (OOWS), an automated software production method for Web applications. OOmFPWeb is evaluated on a range of performance-based and perception-based variables, including efficiency, reproducibility, perceived ease of use, perceived usefulness and intention to use. The results show that OOmFPWeb is efficient when compared to current industry practices. Furthermore, the method produces consistent functional size assessments and is perceived to be easy to use and useful by its users.