The calculated distance (air line) between Montesson and Conflans-Sainte-Honorine is approximately 7 miles respectively 11 kilometers.
By car or train, the actual journey to Conflans-Sainte-Honorine is certainly longer, as only the direct route (as the crow flies) between Montesson and Conflans-Sainte-Honorine has been calculated here.
Air line (approximately)
11 kilometers
6 nautical miles