Benedict Leonard Calvert, 4th Lord Baltimore, was born in 1679 in Maryland. He was the oldest surviving son of Charles Calvert, 3rd Lord Baltimore (1637-1714/15). His mother was Jane Lowe Sewall (?-1700). Benedict Leonard Calvert probably had a good education. He married Charlotte Lee (?-1721) in 1698/99. They had seven children.

He was given £600 a year by his father at the time of marriage. He was, nevertheless, was often without much money. He was dependent on Queen Anne for support after his divorce because he and his father were not on good terms. Calvert received an annual pension of £300 and an estimated £1,500 in arrears of customs duties from Maryland about 1714. His father claimed to have paid a large amount of his son's debts and was paying for the education of his grandchildren.

He died on April 16, 1715, at Epsom, Surrey, England. The size of his estate is unknown.