MapMyRun will tell you how far a running route is based on the points you use to plot it. For example, my run on Sunday looked like this when I clicked my way around the route that I ran:
To mix things up, I ran Google My Tracks GPS program on my phone. I was running low on juice, so I turned off the tracking after 1/2 the run, but take a look at the difference in distance heading North:
If the GPS is accurate, I’ve been undercounting my miles by around 10%. Or, it shows that I can’t run straight. Probably a little of both.
The My Tracks program is pretty sweet. The running routes can be exported from the phone to Google Maps, Google Earth, or other mapping sites like MapMyRun in a few clicks.