The eastern portion runs from SR 15 and the Ohio state line; it is approximately 50 miles (80 km) long.

In it entire length SR 218 passes through seven counties while covering over 91 miles (146 km).

While heading southeast the road crosses a railroad track before bending to become east-west.

SR 218 turns south concurrent with US 31, passing east of Grissom Air Reserve Base, before SR 218 turns east, while US 31 continues south.

After US 31 SR 218 enters Bunker Hill, making several sharp turns with in the town.

Past Bunker Hill the road heads east passes through rural Miami County, before turning to become north-south for about half a mile.

[1][3][4] The eastern segment begins at an intersection with SR 15, on the south edge of La Fontaine.

SR 218 heads east passing through farmland in rural Wabash County.

[1][3][5] SR 218 heads southeast, leaving Warren, before bending to become east-west at the Huntington-Wells county line.

East of Berne the road passes through rural farmland, before curving towards the southeast.