The calculated distance (air line) between San Agustín Acasaguastlán and Petapa is approximately 50 miles respectively 81 kilometers.
By car or train, the actual journey to Petapa is certainly longer, as only the direct route (as the crow flies) between San Agustín Acasaguastlán and Petapa has been calculated here.
Air line (approximately)
81 kilometers
43 nautical miles