He was the grandson of Oliver Cramer and his wife Hester, sister of Marmaduke Coghill, Chancellor of the Exchequer of Ireland.
In 1775 he succeeded to the Coghill estates on the death of his cousin, Hester, daughter and heiress of James Coghill and widow of Charles Moore, 1st Earl of Charleville.
The same year he assumed by Royal licence the surname of Coghill in lieu of Cramer.
[2] In 1778 he was created a baronet, of Coghill in the Baronetage of Great Britain.
He was succeeded in his title by his eldest son, also called John.