The calculated distance (air line) between Chalfont St Giles and High Wycombe is approximately 8 miles respectively 12 kilometers.
By car or train, the actual journey to High Wycombe is certainly longer, as only the direct route (as the crow flies) between Chalfont St Giles and High Wycombe has been calculated here.
Air line (approximately)
12 kilometers
7 nautical miles