A new proposal is given to design a spin half‐adder in a nanojunction. It is well known that at finite voltage a net circulating current (known as “circular current”) appears within a mesoscopic ring under the asymmetric ring‐to‐electrode interface configuration. This circular current induces a finite magnetic field at the center of the ring. Herein, this phenomenon is utilized to construct a spin half‐adder. The circular current–induced magnetic field is used to regulate the alignments of local free spins; by their orientations the output states of the “sum” and “carry” are specified. All the outputs are spin based; therefore, the results get atomically stored in the system. The experimental possibilities of the proposed model are also illustrated.