Running Time Calculators

Have you ever plugged a race time into a running calculator website?  After a recent discussion with members of my running club, I decided to do this.  We were talking about goal marathon times vs. projected marathon times.  Theoretically, the running calculator works best when you have recent results to put into the "machine" to calculate.  This worked out well for me, since the majority of my PRs have come within the past five months or so. 

From these predictions, I can make a few assumptions:

• Either all the stars were aligned when I ran my 5k PR and have not been able to do anything that great since, or I am not running to my full potential given that PR
• My 10k PR should be faster.  This makes sense, since the time I plugged in was from Ragnar and not an actual race.  I did not taper for Ragnar, so I can assume if I taper then the time will decrease.
• I think my marathon times are a little ambitious...I have never ran a marathon before and complete my first one in those times would be a near miracle in my mind.
• This is just a computer, giving me feedback, and does not take into account a lot of other running variables, such as weather, preparation, determination, sleep, injury, and so on.

The bottom line is that this website is just a guide for how it thinks you should be running.  Sometimes guides are right, and other times they are wrong.  Sometimes you have good races, and other times you have not very good races.  I just find the whole thing rather fascinating. 

Have you ever put a race time in a running calculator to see what you "should" run for a different distance?  Was it accurate?