Last Sunday on the weekly LSR, I got to talk with a follow runner that was about to run his first Marathon in 2 months time. The subject was how to find the correct Marathon pace, and it turned out that most of us on the group had wildly different rules as to how to find the correct or optimum pace.

We came up with the following list of methods and I wonder if any of you have anything specific to say about them. (Yes, I do know that is not a proper Q&A, but I have no ideas where else to ask the question...) Assume that you have run a half-marathon at 1:45:00 (=4:57 min/km)...

* We had "double the distance, means add 13 sec/km or 20 sec/mile" (no official reference, but see [Runners World](http://www.runnersworld.com/running-tips/ask-coaches-finding-half-marathon-pace)), which gives 5:10 min/km (=3:38:00).
* We had "2\*HM+20 minutes", which gives 3:50:00 (=5:27 min/km).
* Run for 60% HRR, which for me would give 5:25 min/km (=3:48:00)
* We had "age-grade is constant", which would give 3:39:00 (=5:12 min/km) (see this [calculator](http://www.runningfreeonline.com/Tools/Running_Age_Grade_Race_Calculator) for numbers). The idea here is that if you run at the x% of the speed of the fastest HM runner at your age, then you can do the same for the fastest Marathon runner also your age.
* We had [Pete Riegels formulars](http://www.runscore.com/coursemeasurement/Articles/ARHE.pdf), which gives 3:38:00 (=5:10 min/km). I have used these via SportTracks for some years, and testify that they are somewhat optimistic unless you really are doing an all-out effort.
* We had "VO2max is constant" method based on [work by Daniels and Gilbert](http://www.had2know.com/health/vo2-max-calculator-racing-daniels-gilbert.html), which gives 3:38:00 (=5:10 min/km).

Although the methods are rather different (at least as I seem them), they tend to give almost the same results: either 3:38:00 (=5:10 min/km) or 3:50:00 (=5:27 min/km). I have no doubts that the later speed will give a more comfortable and sure run with little risk of injury whereas the former will probably give some sore legs for the next week.

How would you rate these methods? Should we tell our fellow runner to go for the fast pace (he is young and confident of himself) or the slower pace?