The calculated distance (air line) between St Albans and Chalfont St Giles is approximately 13 miles respectively 21 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 St Albans and Chalfont St Giles has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles