Abstract: A clamping device adapted to be secured on the wrist of a person and conformed to retain portable calculators of various sizes thereat. In a first embodiment the clamping device comprises an angulated base plate including wrist band receiving slots along the lateral edges thereof and provided with an outwardly extending longitudinal securing lip. The base plate surface subjacent the wrist band furthermore, includes two transverse surface recesses conformed to receive at various depths of insertion, two parallel tongues extending from a locking plate similarly provided with a longitudinal retaining lip. Both the tongues and the recesses and the interiorly opposed surfaces of the locking lip each include longitudinal serrations biased to maintain the calculator in position and to provide an engaging interface. In a second embodiment a single, unitary, structure is utilized to form the base plate, such base plate including two spirally wound longitudinal edges which by spring deformation retain the calculator.