Primarily a tropical distribution from the central and western Pacific, including Vietnam and China, to Madagascar and Reunion Island in the western Indian Ocean. In Australia it has been documented from Western Australia, northern Australia, and eastern Australia, including Lord Howe Island.
Observed in intertidal and shallow subtidal zones to depths of 20 m. Individuals sometimes assemble on branches of living coral but can be seen amongst coral rubble and rocks. It inhabits numerous species of small gastropod shells.
Calcinus guamensis can be easily distinguished from all other species of Calcinus by its distinctive colouration: it is the only known species with black areas on the proximal surfaces of the dactyls of periopods two and three, the distal halves of the meri and most of the carpi of both chelipeds, and on the middle, dorsal surfaces of the eyestalks. It grows to a maximum shield length of around 12 mm, total length 40 mm.