302-7.102—How is the mileage distance determined under the commuted rate method?

To determine the distance from the authorized origin to the authorized destination, the Household Goods Carriers Standard Mileage Guide, or a standard road atlas issued by The Household Goods Carrier's Bureau, or any other mileage guide authorized by your agency.

Code of Federal Regulations

Note to §§ 302-7.100 and 302-7.102 : Any substantial deviation from the distances shown in the authorized mileage guides must be explained on the travel claim.