The road begins in Guildford at the start of Farnham Road near Guildford Station, coming out of the town and passing over the A3 where shortly after it becomes a dual carriageway running in a westerly direction along the Hog's Back escarpment of the North Downs. At Tongham it leaves the older Hogs Back route to join with the A331 and follow a modern bypass round Farnham, rejoining the older route at the roundabout junction with the A325 where it follows Alton Road toward Alton which it bypasses, rejoining the older route near Jane Austen's house, then continuing to Alresford before joining the route of the M3 motorway at its junction on the eastern boundary of Winchester.