|Length:||149 mi (240 km)|
From the M4 motorway Junction 42, just east of Swansea, it travels west along the Fabian Way towards Swansea where it turns to a northwesterly direction towards the M4 motorway junction 47 at Penllergaer after which the route is multiplexed with the A48 along Swansea Road, Bryntirion Road, Bolgoed Road to Pontarddulais.
After Pontarddulais, the route continues along Heol Fforest and Carmarthen Road. The A483 diverges from the A48 at the final M4 motorway junction, Junction 49, where it continues via Ammanford, Llandeilo and Llandovery.
The A483 continues through Llanwrtyd Wells, Builth Wells (where it crosses with the A470) and Llandrindod Wells. It then reaches Newtown where it passes under the Cambrian Line at the Dolfor Road Railway Bridge. This bridge, being 13' 3" has been hit by high vehicles on many it occasions. The road then continues to Welshpool before entering England.
As the road enters Wales again, junctions are numbered, starting with junction 1 at Ruabon when the road becomes a dual carriageway, which it remains as until the junction with the A55 at Chester. The A483 then continues past Wrexham and Gresford (the B5101 road is linked to the northwest in the west of Wrexham) before sloping onto the Cheshire plain and re-entering England; as it does so, junction numbers end at Junction 7 at Rossett just before the English border.
The road then enters Cheshire to end at Chester. Discussions have taken place to make the route from Ruabon to Oswestry a dual carriageway, as part of a plan to dual the route from Wrexham to Shrewsbury (part of which is the A5 road) in an effort to increase transport links with the M54 motorway.