The calculated distance (air line) between Sint-Pieters-Leeuw and Charleroi is approximately 27 miles respectively 43 kilometers.
By car or train, the actual journey to Charleroi is certainly longer, as only the direct route (as the crow flies) between Sint-Pieters-Leeuw and Charleroi has been calculated here.
Air line (approximately)
43 kilometers
23 nautical miles