It starts at a double set of traffic lights on the A5 in Maida Vale. It heads roughly west along Clifton Road to Warwick Avenue tube station and the unusual St Saviour's church. Here it TOTSOs right at a mini-roundabout into Warwick Avenue before turning left at the next mini-roundabout into Formosa Street then right again at a third mini-roundabout into Shirland Road.
After all that zigzagging the next half mile of the B413 is quite straightforward: continue straight along Shirland Road. It crosses Sutherland Avenue and Elgin Avenue at traffic lights before meeting the B414 end-on. That road TOTSOs north into Kilburn Park Road and the B413 multiplexes with it for nearly half a mile.
Originally the B413 took the next turn right into Malvern Road. This is now unclassified and closed to through traffic, hence the multiplex that exists today.
After going past Paddington Recreation Ground, the B413 regains its number by turning left at traffic lights. It heads west along Carlton Vale to meet the northern end of Malvern Road just before a roundabout by Queen's Park station. The B413 continues west along Kilburn Lane parallel to the railway line and ends at traffic lights on the B450 Chamberlayne Road in Kensal Green.