The calculated distance (air line) between Kwaadmechelen and Sint-Niklaas is approximately 44 miles respectively 70 kilometers.
By car or train, the actual journey to Sint-Niklaas is certainly longer, as only the direct route (as the crow flies) between Kwaadmechelen and Sint-Niklaas has been calculated here.
Air line (approximately)
70 kilometers
38 nautical miles