The calculated distance (air line) between Sępólno Krajeńskie and Gdynia is approximately 84 miles respectively 135 kilometers.
By car or train, the actual journey to Gdynia is certainly longer, as only the direct route (as the crow flies) between Sępólno Krajeńskie and Gdynia has been calculated here.
Air line (approximately)
135 kilometers
73 nautical miles