A gas cylinder tank storage rack uses groups of load cells to sense the presence and fill state of tanks in storage locations on shelves. Tanks can be stored lying down horizontally on parallel rails. The rails are hinged to a crossbar of a frame of the rack and rest at an opposite end upon load cells attached to another crossbar of the frame. Multiple tanks can also be stored upright upon platforms resting upon at least one pair of load cells affixed to front and/or back crossbars of the frame. Sensor outputs from pairs of cells are processed in tandem to yield an average load value. The measured load in relation to threshold values determine the number and fill state of tanks on the shelves. Tank inventory can be communicated to a server to handle ordering of replacement tanks when needed.