So I'm just short of two weeks from my first marathon in over 14 years and I'm wondering how fast I can and should run it.

I've only ever run one marathon, the one I needed to do one to gain entry into Two Oceans marathon, and it was a terrible performance in which I got caught up with the half marathon runners that started at the same time and I crashed and burned just past half way. I finished, but not in a time worthy of screaming from the rooftops... 4:11 which is terrible when you consider my beautifully paced Two Oceans (56km) time of 4:48.

Since then, I've not raced anything further than 32km since, so I really don't have any recent marathon efforts to go on and thus I have to base my predictions on my performances over shorter distances.


One of the most popular formulas to use is Pete Riegel's formula (first published in Runner's World and still used in this calculator)...

t2 = t1 * (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.

I won't explain the formula, you can read more about it here, but I will say it is just a model. A very good model, but not a 100% reliable and precise model.

Anyway, if I take my best time for the distance closest to the marathon, the half-marathon at 1:19:53, and bung it into the calculator on Fetchpoint I get ...

DistEstimateActual PB
5k17:2217:36 1
10k36:1237:55 2
10M59:571:01:15
21.1k1:19:491:19:53 3
42.2k2:46:24- - 4

So if we take into account the notes, not a bad predictor for me, but look at the marathon time... 2:46!? Really!?

OK, I'll let you into a secret, I discovered this earlier this year and it's been on my mind ever since. Now I've not done much in the way of desired marathon paced training as I'm testing to see if my success last season with MAF carries over to the marathon this year, however I have not been doing MAF exclusively. I've also been doing one marathon specific speed session... Yasso 800s.

Now the idea behind Yasso 800s is you do 800m intervals at the m:s time of your desired marathon's h:m time with 400m recovery between each. Each 400 is covered in the same amount of time as the 800s. Now the theory goes that it your regularly run 100+ km weeks and you can do 10 of these reps all at the desired pace, there's a good chance you're in shape to run your marathon in your desired time.

Well, yesterday I did my last Yasso 800s session and completed all 10 at my desired pace of approx 2:44-2:46/800m with 400m recovery in about 2:45 and I'm chuffed to bits, however I'm not confident about this 2:46 + "a few minutes" marathon I'm supposed to be capable of.

I think I'm in great form, but can I really do it? It would be brilliant if I could and push it under 2:45 too as dipping under 2:45 means I can start the London Marathon with the elite men (I'll stand a long way behind Mo Farah 😉). That said, I don't think I'll being finding out if I can on 6 May as I have one goal for this marathon: run sub-3:15 so I can qualify for next year's London Marathon by the "Good for Age" route. I'm actually gunning for sub-3 as I think I can do that, however I don't want to blow it gunning for an almost impossible time... 42.2km is a long way to run and get it horribly wrong.

I'll certainly push things a bit if everything is going really well at the halfway mark. I think I'll leave the experimenting for the Abingdon Marathon in October. Who knows, maybe I can get a 2:46-ish time then when I'm a little more confident. 🙂