Today it is easy to upload or download files to and from Web servers or file servers on the Internet. However, it is difficult for users to select the optimal server because these servers rarely disclose their performance specifications or current processing loads. In order to select the optimal server for user, there have been many studies in server side approach, but not so many studies in user side approach. Therefore, some novel indicator that enables the user to select the optimal server is desired. For this purpose we propose to use a pilot file that is small enough to be downloaded quickly. The proposed method is compared with the conventional method, which measures the round trip time between the user and the server. The effectiveness of these methods is demonstrated in this study. The possibility for these methods to estimate the time to download a target file (which a user desires to download) is also discussed.