The calculated distance (air line) between Bushey and Chalfont St Giles is approximately 9 miles respectively 15 kilometers.
By car or train, the actual journey to Chalfont St Giles is certainly longer, as only the direct route (as the crow flies) between Bushey and Chalfont St Giles has been calculated here.
Air line (approximately)
15 kilometers
8 nautical miles