The calculated distance (air line) between Leighton Buzzard and Chalfont St Giles is approximately 20 miles respectively 32 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 Leighton Buzzard and Chalfont St Giles has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles