The calculated distance (air line) between Stratford-upon-Avon and Swansea is approximately 103 miles respectively 166 kilometers.
By car or train, the actual journey to Swansea is certainly longer, as only the direct route (as the crow flies) between Stratford-upon-Avon and Swansea has been calculated here.
Air line (approximately)
166 kilometers
90 nautical miles