I’ve found the McMillan running calculator it be pretty good at predicting my time over certain distances. In training I’ve completed 25K in 1:42, so the calculator projects my marathon time at 2:59. My question is this: is the calculator assuming that I will reach the 25K mark at 1:42 (during the marathon) or is the calculator simply saying that based on my past performance I “should” be able to finish the marathon in 2:59?
It probably means that you go slower at 4:15 per Kilometer all the way, but based on the statistics, there are few that will achieve this :-). This pacing would put you at 25K at 1:46.
You are supposed to input your best RACE time at a given distance, then it calculates the equivalents. If you think the fastest you could race 25k is 1:42, then with the proper training it is saying you can probably do about 2:59 for a marathon.
If you still had a good deal left in you after the 25k training run and think you would race such a distance faster than 1:42, you should use that faster time with the calculator (e.g. 1:40 if you think you would cut at least two minutes off the 25k time if you were “racing” it, not on a training run).
If you have done any races this year, try out those times/distances as well, see if the results are similar.