The calculated distance (air line) between Le Mesnil-le-Roi and Sannois is approximately 6 miles respectively 10 kilometers.
By car or train, the actual journey to Sannois is certainly longer, as only the direct route (as the crow flies) between Le Mesnil-le-Roi and Sannois has been calculated here.
Air line (approximately)
10 kilometers
5 nautical miles