The calculated distance (air line) between Dehiwala-Mount Lavinia and Vavuniya is approximately 139 miles respectively 223 kilometers.
By car or train, the actual journey to Vavuniya is certainly longer, as only the direct route (as the crow flies) between Dehiwala-Mount Lavinia and Vavuniya has been calculated here.
Air line (approximately)
223 kilometers
121 nautical miles