Starting at Marble Arch, it runs north west up the Edgware Road. The A5 as numbered disappears near Edgware, but re-emerges south of Luton. However, the road itself continues as the A5183 from Edgware to Elstree, Borehamwood, Radlett, St Albans and Redbourn, to junction 9 of the M1, where it becomes numbered as the A5 again. It then travels through Dunstable, Milton Keynes and Towcester, near Rugby and Hinckley, then through Tamworth, Cannock and Telford. After bypassing Shrewsbury and Oswestry, it enters Wales and continues through Llangollen and Betws-y-Coed. The road then crosses the Menai Strait near Bangor before arriving at the port of Holyhead.
Parts of the A5 have been superseded by sections of the M1, M54 and M6 Toll motorways.