The calculated distance (air line) between Mīr Bachah Kōṯ and Khōst is approximately 108 miles respectively 173 kilometers.
By car or train, the actual journey to Khōst is certainly longer, as only the direct route (as the crow flies) between Mīr Bachah Kōṯ and Khōst has been calculated here.
Air line (approximately)
173 kilometers
94 nautical miles