The calculated distance (air line) between Jēkabpils and Daugavpils is approximately 50 miles respectively 80 kilometers.
By car or train, the actual journey to Daugavpils is certainly longer, as only the direct route (as the crow flies) between Jēkabpils and Daugavpils has been calculated here.
Air line (approximately)
80 kilometers
43 nautical miles