Similarity measurement between web services is a key solution to benefit from the reuse of the large number of web services freely available in the internet. This paper presents a practical approach that enables an effective measurement of web service similarity based on their interfaces descibed with WSDL. The approach relies on the use of multiple matching techniques and different semantic and structural similarity metrics. The measurement of similarity determines the best substitute for a failed web service. So, it serves as a good indicator of the substitutability relation and thus of the capacity for reuse. A support tool, implementing the approach, is also presented with some experimental results conducted on real-world web services.