Abstract: The present disclosure provides a simple dumbbell including a dumbbell rod, an adjustment component, and a dumbbell piece. Two semicircular telescopic rods are provided in the dumbbell rod, a square groove is provided in a middle of the two semicircular telescopic rods. A square rod is provided on the square groove, a fix hole is respectively provided at two ends of the square rod. A limit tooth is provided on the semicircular telescopic rod; the adjustment component includes an adjustment arm and a locking component. A connection hole is provided in a middle of the adjustment arm, a connection component connecting to an installation seat is provided in the connection hole. An adjustment area is provided below the adjustment arm, the adjustment area cooperates with the locking component to adjust the semicircular telescopic rod; the dumbbell piece is provided on an outer side of the adjustment component.