The calculated distance (air line) between Dehiwala-Mount Lavinia and Kalmunai is approximately 140 miles respectively 226 kilometers.
By car or train, the actual journey to Kalmunai is certainly longer, as only the direct route (as the crow flies) between Dehiwala-Mount Lavinia and Kalmunai has been calculated here.
Air line (approximately)
226 kilometers
122 nautical miles