Abstract: A self-contained magazine for a firearm includes a housing for receiving a plurality of rounds therein, the housing including an open end through which rounds are loaded and unloaded, a follower provided in the housing, said follower being slidable along a longitudinal axial direction of the magazine, a spring biasing the follower toward the open end, to bias rounds toward the open end, an electronic counter means integrated in the magazine for calculating the number of rounds contained in the magazine upon loading rounds into and unloading rounds from the magazine, and display means for displaying the number of rounds in the magazine. The present invention provides a self-contained magazine for a firearm that incorporates all essential features for calculating and displaying the number of rounds therein as the number changes due to loading and unloading.