Calmacil was the second son of Atanatar II Alcarin and the eighteenth King of Gondor. He took the throne from his childless brother Narmacil I, but, like him, he also left Minalcar, his son and the Regent of Gondor, to actually rule the realm.

Calmacil was King for 10 years, from TA 1294-1304, and he was succeeded by his son, Minalcar, better known as Rómendacil II.