Predicted Marathon time

2:50 sounds about right. I ran 3:05 when I was 18 and I ran 17:12 5k xc in high school. You problably have potential for 2:35-2:40 but at your age and experience its not likely.

Good Luck.

Your times indicate that you have the talent to run faster and the fact that you are willing to put in the mileage indicate that you should run faster. My only question would be if you might consider targeting a half marathon or run some 10k-10miles and then target the marathon after that. This is not because you can't handle the prep, simply because the feedback from those longer races will enable you to ultimately be more successful in the marathon. Either way, good luck.

A 2:50 marathon is 6:29/mile pace. If you can do your long runs (20-23 miles; 25 mile is too long) at 7:00/mile pace or faster, then it is a reasonable goal. Personally, I think you'd go much faster than 2:50 with that kind of mileage.

Also, don't understimate the number of potential problems that could arise at a marathon. Here are some questions to ask yourself:

Is temperature/humidity going to be substantially different from what I'm used to?

Can my body handle the provided sports drink?

Will I have problems with allergies (i.e. pollen, smog)?

Best of luck in your training.

i've never come near those times and i've run 2:42 off less milage.

I ran a marathon a couple weeks ago and im 19, My 5k pr is a little slower than your. I did the milage and the long runs, and I came into the race In the best shape of my life looking o run at least sub 2:50, anyway I went out way too fast (1:01 the frst 10miles) , Around 22miles My quads locked up, and I stumbled into a 2:58 marathon with a 27min last 5k. So Make sure you Play i alot safer than you expect. Break it up into a 20mile long run with a 6.2mile race. If you do this, 2:50 or better is a resonable goal.