# The RW Race-Time Predictor

261 to 271 of 271 messages
21/10/2013 at 09:50

Might the predictor require some tuning ?

If I enter 21.0975 (half a marathon) and 1:20:10, the reply for 42.195 is 02:47:08.

According to the explanative text, I would have expected (1:20:10)*2*1.06 = 2:49:57?

The answer 2:47:08 looks like the coefficient would have been 1.0455 instead of 1.06?

21/10/2013 at 09:52

(cancel and replace) oops, I missed the point! The formula is (^power)1,06 and not (*multiplied by)1,06.

10/07/2014 at 23:50

What FrdricLN said, the formula is good, but it is stated incorrectly, it is to the power of 1.06, not multiplied by it as stated.

11/07/2014 at 00:16

congratulations for clearing up a 8 month mystery!

12/10/2015 at 08:28

So, I have done 19.5 miles in 3hrs 16 and this says my marathon will be 4hrs 28 ?

Having done almost 20 miles in approx. 3hrs 15 it will suddenly take me 1hr 12 to do 7 miles?

I doubt it!

12/10/2015 at 09:13

Why do you doubt it? You want to do a third more distance (26.2/19.5=1.34) so if you didn't tire whatsoever and ran a flat pace you'd need another 1:05. You get the same answer if you feed the expression into google search bar, i.e.:

196 * (26.2/19.5)^1.06=

i.e., 268 minutes or 4:28. So the calculator is working. The exponent varies a bit from person to person.

12/10/2015 at 09:32
@doubleohdave
Sounds spot on to me TBH. If you did 19.5 in 3:16 thats a pace of just over 10:03. There are another 6.7 miles in a marathon and to do in 4:28, if you were to run at end of your 19.5 you'd have to run them in 1:12, or 10:44 pace.

If you ran your 19.5 for the best possible time you should be exhausted at end and certainly unable to run another 6.7 only 41 seconds a mile slower than your avrage over the previous 19.5...remember you hadn't even reached 20 miles and its usually after that most get into trouble (or as they approach it and realise they're struggling 8 miles from home).

It may be that you were fresh as a daisy at end of 19.5 and could have run the remainder at the same pace, but thats not comparing like with like, one run would be slow training run, thenother (marathon) you'd have pushed on relativley harder. No calculator can account for that. Also you'd run the longer distance (if you had sense) slower from the start rather than slowing down like that.

But beware that last 10k, is a killer and those who undrestimate it end up in trouble.

FWIW I've found this calculator spot on for me.
12/10/2015 at 11:50
DoubleohDave? Was this 19.5 miler a race effort or a training run.
If it was just a training run then it's like comparing apples and oranges.
Also, if it was a training run, are you running then at target marathon pace?
13/10/2015 at 12:55
This calculator is a bit better. It allows you to use 2 results to create your wn co-efficient(multiplier) and gives you a time based in that.

08/02/2016 at 14:22

It works bang on for me. From 5K to HM, I am routinely within 10 seconds of the predicted time from a recent race. If I have a good marathon, I'll be within 30 seconds of the prediction.

15/12/2016 at 17:44
Impressive. Entered my recent 5k PB time and asked for a 10 mile prediction. Result was 1 second slower than a recent 10 mile race time I completed and also recorded a personal best. Nice

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261 to 271 of 271 messages