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# The RW Race-Time Predictor

Hello all

we'd love to know whether this calculator (click the link above) matches your real-life race times.

It's based on a well-established formula - what do you think?

My first reaction was that its predictions were too fast, but I think that was because
a) I have a bit more speed than endurance; and
b) my instinct was to try to predict times at the extreme ends of the distance spectrum (eg marathon time from 5K time)

Sean, RW

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Well, it thinks that I should be about a minute faster over 10k than I've ever run. That's probably about right though as I'm better trained for endurance and prefer racing longer distances.

I very much hope it's accurate, because it's tipping me for a 2:53 marathon ;o)
• Seems pretty accurate for me, but my 10k time is quite slow for my marathon time compared to a lot of other people's.
• It thinks I should be slower over 10K than I actually am. This is based on 10 mile and half times.

About a minute out from my PB of 36:58, based on a 10 mile time of 1:02:43.
• I think it works pretty well - my 10K PB predicts a half-marathon time less than a minute quicker than my actual best half. Frustratingly, the two half-marathon times are either side of my goal of 1:45! So, there's hope!

I have a copy of this formula in my running log to give me an idea of how easy or hard a run really was - every run is converted to a predicted time for a half-marathon so that I have a standard to measure against.
• My 10m time would predict a sub 2:40 marathon, though reality is different, 12 minutes behind. Based on shorter distances, I ran faster times than predicted.
• It's great news for me because my 10k PB of 42:28 predicts my marathon time as being 3:15:09 and as I'm going for sub 3.15 in 5 months time, it's an indication that providing I get the training is, I should achieve it without too much difficulty...
• Works within parameters give or take a couple of minutes on the marathon time
• I suppose that what it doesn't take into effect is that each race is different. So its an indication only. That's unless your running around a track.
• Also if you use it to predict 10K from a 400M time then its waaaaay off.
• yes, the formula was found to work best for 3.5 mins to 4hrs - (or 230 mins to be precise). I think it mentions that on the page
• aaah I never read instructions!
• URR, I knew you were in 2:40 shape:)

Well according to my recent marathon I'm in 35:17 10k shape - let's see if we can take a couple of secs off that on Sunday;)

My 10k pb predicts a sub 2:35 marathon - lol!!
• Just input a recent run I did for 13.1 miles, not a race but just ran a bit faster than normal, RW predicts a 4.48.49 marathon time yet the mcmillan predicts 4.52.10, about 3 and half mins difference!! My marathon PB is actually 5.11.

Both times do fit in with my aim to do 11 min miling for my next marathon.
• the only time i could put in as an official time is a ten miler this predicts a 10k time of just over 52 mins i need to do a 10k to see if i could do it a bit quicker than that hopefully
• It's accurate to one second for 10K/half, but not really for marathon.

A 2:53 marathon from a 37:42 10K seems a bit aggressive.
• It's pretty accurate although it seems I've still got a bit more room for improvement over the longer distances going by my 5k time. It predicts a marathon of 3:12:16, something to work at then for FLM:o)
• Sean, check out my post on the 2:30 thread here

http://www.runnersworld.co.uk/forum/forummessages.asp?UTN=36728&URN=11&dt=4&srchdte=0&cp=23&v=6&sp=

which I did a few days ago. It shoes how to test the relationship between your times. For my 5k, 10k, 10M and HM times the relationship is Riegel's exactly but with 1.0508 instead of 1.06. The r-squared value of the relationship for my pbs is 1 which is the real proof in Riegel's hypothesis when applied to me.
• Nice stuff, Mike. Do you mind if I lift that into a 'find out more' page?

Have you seen this race-time ranking calculator on RW US? It's a hidden link that has now been replaced by 'under construction' message on the front of their site, so I'm not sure what's going on there.

That's another one to adapt for the UK
• Mine get steadily worse the longer I run. Maybe I haven't done a flat marathon or half yet to compare though.

• doesn't work for me

my half marathon "should" be faster than my PB even if I enter my PW 10k time

• seems about right for me, using my known training run times (not raced properly yet).

Rather interesting to see that should I ever do a complete U-turn and actually try a marathon, that I'd be on for five hours, when I thought it would be much nearer six...
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I'll get back to you you on that
according to 10k time should take 30 seconds of 5k best (not run since sept) and 8 minutes of my half (last one was in June)
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Almost spot on for all distances from 5k to half marathon, though it seems I am 5 mins too slow for 20 miles and 8 mins too slow for a marathon.

Personally I find that most race time predictors are too optimistic for the longer distance races.
• Same for me - it works well for distances 5k to half marathon. But much as I would love to run the predicted 2-51 for a marathon, that's 10 minutes faster than I've actually managed.
• I also found it quite accurate for distances 5k to 1/2m, however the marathon prediction calculates a time of 2 x 1/2m time + 6mins which I think is a bit optimistic. I've always thought that 2 x 1/2m time + 10mins is a good prediction of marathon potential.
• The marathon time is faster than I've ever managed, too.

I wonder if most of us are just under-developed in terms of endurance (compared with speed). Certainly when Riegel first came up with the equation in the late 1970s, I guess the norm was towards training at much higher mileage than now.
• I do suspect - without wishing to offend anyone - that most people d onot enough run enough miles to fulfil their marathon potential. I've always felt that training for any distance from 5k to 1/2m is pretty much the same, but marathon training is a completely different ball game.
• Like the others it doesn't work for me.

Current form : 10k and HM in last 3 weeks - HM should have been 8 mins quicker

PB form in the Spring - HM should have been 5:30 quicker - 97 secs off that 90 min barrier, whereas in reality I'm a whole 7+ minutes away!
• Surprisingly accurate for me, I'd say, Sean. I noticed the caveat is that you've done the adequate training and don't have any bias - well, I think I have a bias for shorter distances so I put in my Brighton time 44:58 and checked back to 5k. It gave me 21:34. A few days previous to Brighton I did 5k on the treadmill on 2% incline and got 21:19.

I've discovered that up to about 5k road is faster than TM on 2%, after that it goes the other way. 10k I have to add 1 min. I think it's something to do with the stride length?
• It confirms to me how much I messed up my fist half training this year - gives me hope for a good chunk off next year (even if I don't hit the predicted fig) s'long as I can get my act together. :-)))