A new modeling tool GRcut was developed to be used for atomistic simulation of isolated nanoparticles. It generates atomic coordinates in crystalline nanoparticles with equivalent crystallographic surfaces. In addition to 32 crystallographic point groups, nine non-crystallographic point groups with five-fold symmetries are implemented for modeling icosahedral and decahedral clusters in a systematic way. Curved surfaces with spherical, ellipsoidal and cylindrical shapes in arbitrary orientation are also available. This software is useful as a pre-processing tool for molecular simulation on metallic clusters, quantum dots, or fullerenes in high symmetries. The GRcut is distributed as a Java applet via the Internet to be used on web browsers.