A calculator that is selectively attachable to an article attached to a user of the calculator is disclosed. The calculator has an oblong carabiner extending from its bottom end for attaching the calculator to the article. The attachment mechanism includes an oblong loop and an arm that is part of the loop. The arm is rotatably attached to the loop so that the loop can be opened and closed to permit attachment to the article. The arm is biased to the closed position. The attachment mechanism is disposed so as to permit the user to read symbols on input buttons and an output display in the right-side-up position, while the calculator is attached to the user.