Is your stomach talking back to you Quiet your tummy with Rugby Calcium Carbonate. This antacid formula relieves acid indigestion heartburn sour stomach and upset stomach associated with these symptoms. Calcium Carbonate 648 mg 1000 Tabs - Is your stomach talking back to you Quiet your tummy with Rugby Calcium Carbonate. This antacid formula relieves acid indigestion heartburn sour stomach and upset stomach associated with these symptoms. Each tablet contains 648 mg of calcium carbonate 10 gr.