Abstract: A device for accurate measurement based on wire diameter includes a clamp and two-space compensators. The clamp includes depressible grip handles to control opening and closing of two measurement sections. Two space compensators are respectively combinable with the two measurement sections. The space compensators each have a side that is recessed to form a first clamping section, such that the first clamping section is combinable with at least two fixing elements, which are each in an arc curved shape having one side recessed to form a second clamping section. The fixing elements are structured such that inside diameters defined by the second clamping sections thereof are reduced one by one in a direction away from the first clamping section. The fixing elements are selectable to have the inside diameter of the second clamping section matching a size of an electric wire to be measured.