When I signed up for the Portland Marathon in June 2013 they asked what I thought my time would be. (so they can start me with others about the same)I really had no idea so I took my half marathon time (2 hour 30 min) multiplied by 2 and added about 15 minutes, which would have put me in about 5 hours 15 minutes. I figured if the stars aligned I could possibly make it in 5 hours, but anything between 5- 5:30 would make me happy. After all it was my first time running 26.2 miles and it was about the distance, not the clock.
When I saw this after I got home I thought all was going well until mile 25! That was when my IT band started hurting.
My finish time was 5:33:22 so I was close to what I hoped for.
This information comes from my Nike Running App for my phone. I recommend it highly if you like to track your walks or runs.