Is there some sort of calculator 'out there' where one (Ok, me) can put in airport codes, or city codes, for a routing. To see how many miles the trip should be (Approximations of course).

I have been finding that some airline web sites readily display this information, and on some, I have to go searching for it.

For example... Say I have the following choices:

LAS-DFW-ATL-BWI Or LAS-LAX-BWI