Projected Finish Times

The other day I ran 7 miles in 56 minutes, right at 8:00 minute mile pace. I was fairly impressed with myself, especially considering the major hills on this particular run. I entered the run into the RunnersWorld.com Training Calculator and here are the results:

Based on a 7 miles race at 00:56:00, your projected finish times for the following distances should be:

the mile 7:07 3000m(3k) 13:47 3200m(about 2 miles) 14:45 5000m(5k) 23:40 8000m(8k) 38:58 5 miles 39:12 10,000m(10k) 49:21 ten miles 1:21:44 a half marathon 1:48:49 a marathon 3:46:52

Well I know I can run a mile much faster then 7:07, and I've ran a 5k faster then 23:40...but I doubt I could run a marathon in 3:46 right now, or even a half marathon in 1:48...Should I give it a try?

The Distance Finish Times calculator calculates a predicted time at a distance for you based on a time you provided for another distance. It uses the formula T2 = T1 x (D2/D1)1.06 where T1 is the given time, D1 is the given distance, D2 is the distance to predict a time for, and T2 is the calculated time for D2.
The formula was developed by Pete Riegel and published first in a slightly different form in Runner's World, August 1977, in an article in that issue entitled "Time Predicting." The formula was refined for other sports (swimming, bicycling, walking,) in an article "Athletic Records and Human Endurance," also written by Pete Riegel, which appeared in American Scientist, May-June 1981.

You can access the training calculator here