You can do it with TrainzMap. It will give you the length of the route. There is also a handy little utility on the DLS that you can measure distance between two points, but I can't remember the name of it off hand. Maybe someone will come along and remind me. It's a very handy little utility where you place two markers on your track where you want to measure distance and it will give you the distance between the two markers. Beware, that if there are yards or passing sidings between the two markers, it will calculate the shortest distance.
If no one comes along, I'll look up what it is.
Mike
Edit: I found the utility for you. Its called Track Scanner by sforget. The kuid is 2:117746:23230:1