The calculated distance (air line) between Šmarje pri Jelšah and Maribor is approximately 23 miles respectively 38 kilometers.
By car or train, the actual journey to Maribor is certainly longer, as only the direct route (as the crow flies) between Šmarje pri Jelšah and Maribor has been calculated here.
Air line (approximately)
38 kilometers
20 nautical miles