Commas is bounded on the north by Alteen townland, on the south by Aghnacollia and Altbrean townlands, on the west by Aghatirourke, Bellavally Lower, Bellavally Upper, Bursan, Dunmakeever and Legnaderk townlands and on the east by Aghaboy (Kinawley), Binkeeragh, Monydoo (or Tonycrom) and Tullydermot townlands. Its chief geographical features are Cuilcagh mountain which rise to 2,188 feet above sea level, Binbeg mountain which rises to 1,774 feet, mountain pools, the River Cladagh (Swanlinbar), mountain streams, waterfalls, underground streams, river swallowholes, ravines, caverns and forestry plantations. Commas is traversed by minor public roads and rural lanes. The townland covers 2,551 statute acres and is the largest townland in County Cavan.