Are you trying to find nautical miles between points for shipping lanes? If so, a site like http://www.marinetraffic.com/en/voyage-planner/ may help. Enter two ports in voyage planner and it shows the routes and provides the nautical miles for the route. Not sure if having an account there allows for batch jobs.
According to calculator-converter.com, the nautical mile (mni) is nearly equal to one minute of arc of latitude along any meridian, and is approximately equal to one minute of arc of longitude at the equator. The nautical mile (nmi) = 1.15077945 statute miles = 1.852 kilometers (km) = 1852 meters = 6076.1155 feet = 2025.372 yards. Once you have the nautical miles, you can now convert to miles using an equation.
If you want more of a straight line calculation that takes the earth's circumference into account, you could use the equation below
=ACOS(COS(RADIANS(90-A2)) *COS(RADIANS(90-A3)) +SIN(RADIANS(90-A2)) *SIN(RADIANS(90-A3)) *COS(RADIANS(B2-B3))) *6371
You could then use the info above to calculate into nautical miles (but assumes no land masses in the way as it is only a straight line move).
Hope this helps,
Thank you for the response Andy. This question is a bit older but the answer is very helpful so I am marking the question assumed answered to assist other users with similar questions.