After graduating with first class honours in 1800, Inman intended to undertake missionary work in the Middle East, in Syria, but due to a declaration of war could travel no further than Malta, where he continued to study Arabic.
In the third edition (1835) he introduced a new table of haversines (the term was his coinage[3][4]) to simplify the calculation of distances between two points on the surface of the earth using spherical trigonometry.
His wife Mary, daughter of Richard Williams, vicar of All Saints' Church, Oakham, Rutland, was a direct descendant of Hannah Ayscough, the mother of Sir Isaac Newton.
Their eldest son was James Williams Inman (1809–1895), Cambridge BA 1833, MA 1836, headmaster of The King's School, Grantham.
[5] In Sir John Franklin's first North American expedition he named Inman Harbour "after my friend the Professor at the Royal Naval College".