Tonna is bounded by the wards of Aberdulais to the north; Resolven to the northeast; Pelenna to the southeast; Cimla and Neath North to the southwest; and Cadoxton to the west.
The geographical limits of Tonna encompass the wards of Aberdulais to the north, Resolven to the northeast, Pelenna to the southeast, Cimla and Neath North to the southwest, and Cadoxton to the west.