SR 172 begins at an intersection with SR 72, northeast of Colbert, in Madison County. It heads northeast to an intersection with SR 98, northwest of Comer. It continues to the northeast and crosses over the Broad River into Elbert County. In Bowman is an intersection with SR 17. Shortly afterward, SR 172 crosses into Hart County. It continues to the northeast until it meets its northern terminus, an intersection with US 29/SR 8/SR 77 in Hartwell.