QoS computation plays an important role in Web service selection. It involves property value preprocessing aspect, user satisfaction calculation aspect, and aggregation of multiple QoS properties aspect. However, little attention has been paid to users participating in QoS computation. In this paper, we examine QoS computation from the angle of experienced users and novice users. An experienced user is able to be more active in providing configuration information such as expected boundary of a QoS property, distribution function of user satisfaction, and the aggregation weight of each QoS property. While a novice user has limited experience to do this. Based on the study of user-centered factors in QoS computation, we propose a user-centered QoS computation, which provides a new choice of normalization in property value preprocessing aspect, an approach of approximation in user satisfaction calculation aspect, and a weight suggestion way in aggregation of multiple properties aspect. A case study in translation service selection shows that the proposed user-centered QoS calculation is more efficient for novice users than random configuration, and much more efficient for experience users.