An adjustable barbell or dumbbell or exercise device includes a handle device having a handle bar engageable into grooves of a number of weight members, a number of plates disposed on the handle bar and engageable between the weight members, and the plates each include an engaging element for engaging with the weight members and for anchoring a selected number of weight members to the handle bar, and a detecting device is attached to the handle device and includes a weight detector connected to a processing unit for sending weighing signals to the processing unit, and a displayer for displaying a total weight of the handle device and the weight members.