The calculated distance (air line) between Dehiwala-Mount Lavinia and Katunayaka is approximately 23 miles respectively 37 kilometers.
By car or train, the actual journey to Katunayaka is certainly longer, as only the direct route (as the crow flies) between Dehiwala-Mount Lavinia and Katunayaka has been calculated here.
Air line (approximately)
37 kilometers
20 nautical miles