Not without pretensions as a man of learning, Charles became a Fellow of the Royal Society and was a member of the court circle. He was twice a member of the Parliament and received marked favours through his friend, Frederick Louis, Prince of Wales, son of George II; he was appointed successively gentleman of the bedchamber to the Prince, Lord of the Admiralty, cofferer to the Prince, and surveyor general of the latter's lands in Cornwell. While traveling on the Continent, he became acquainted with the future Frederick the Great who recorded most favorable impressions of his accomplishments. Other contemporaries have called him an honest, good-natured, but weak man. In his early dealings with the Assembly of Maryland, he exhibited an arrogant spirit but later somewhat redeemed himself by well-considered proposals.

First of the proprietors to visit Maryland in nearly 50 years, Charles came to the colony in 1732 to look after his interests in the boundary dispute with William Penn's sons. He discovered that by agreement made with the Penns in England earlier in the year, he had unwittingly accepted as correct a map whereon Cape Henlopen, one of the principal points in defining the northern bounds of the province, was placed 25 miles south of its true position. The resulting delay in carrying out his agreement gave rise to suit on the part of the Penns to compel performance of the contract. Many postponements dragged the cause out until 1750 when the Lord Chief Justice decided in favor of the Penns. Under this decision long after the death of the fifth Lord, the Mason and Dixion line was established (1767) as the boundary between Maryland and Pennsylvania. For his failure to use proper care against his adversaries, Charles is chargeable with responsibility for loss of part of a territory of several thousand square miles, now included in the states of Pennsylvania and Delaware. In view of his doubtful competence in business affairs and dissolute private life, historians have not accorded him a place among the abler Calverts.

In this fine portrait Charles is shown as a man in his forties, wearing the robes of a peer and holding a scroll. The canvas has been attributed to Allan Ramsey, court painter to King George III.