5k to 10k conversion

Hi all.

I've tried various calculators (runpaces software, mcmillan, fetcheveryone) and got different answers.

I ran 5k in 19:14 this weekend, and have a fairly long-standing target of sub 40 min 10k. Started in back running in Jan with 46 mins, ran 42:25 at Easter. Training has probably been more typical of 10k than 5k.

There are 2 races on the horizon - one in a fortnight and one in November. Both involve a fair travel, so would really only like to do one.

Be interested to know how peoples' times from 5k and 10k compare - the calculators I have used vary from 39:59 (yay!) to 40:36 (boo!). 


  • Hi EC, I recently ran a 39:49 10k off a 19:10 5k the week before so I would say you are pretty much right on the money.

    I guess it depends which race you prefer and which is the quickest course. All things being equal you would probably be about 60/40 to do it in 2 weeks and probably 80/20 in November if you get a solid block of training in.

    Good luck!

  • Probably depends if you have endurance for the extra distance.

    I have 5k 18:57, 10k 38:47, and that should equate to a marathon of 3:01....but my marathon PB is 3:21, possibly because I don't do enough distance in my runs.

  • I reckon you're just about there (other things being equal, blah...) I see one of the predictors is McMillan with 39:57, which is obviously tight but I'm pretty sure the formula they use generates a looser relationship than it used to (i.e. plug in a strong 10k time for me and it will give me a very aggressive 5k target).  Might be worth doing some target pace tempo intervals to see how it feels - see if you can manage something like 4 x 2k or 6 x 1M off 90s recovery.  That'll get your heart going.  image

    Paul - predictors get a lot less reliable when you go from 5k/10k to 10k/marathon because there are different energy systems being used (working way above threshold vs. below threshold but for a very long time), plus so many things that need to go just right to convert up to the marathon distance.

  • McMillan gives you some tough times to hit in general when you go longer race to shorter race.

    And seemingly gives you too soft a target when you key in a short distance to predict your 10m/half marathon

    No idea on marathons...that's a different world of tricky calculations..

  • Exiled

    I'm a 19:29 5k runner and a 40:39 10k runner.

    Both of these PBs are relatively recent and occurred within a month of each other (both off the back of marathon training, rather than focussed speedwork).

    I reckon you should have a go in 2 weeks time.....

  • Cheers for the feedback guys.

    I did a half marathon in July in 1:33:14, on a whim really, without really focusing training on it - longest run was 9 milesbefore it. Got quite a lot of miles in during August (teacher making use of the hols), so think the stamina is there.

    Guess I'll give it a go in a couple of weeks.



  • Mr VMr V ✭✭✭

    Good luck Exile - I ran an 18.53 before my first sub 40 (I actually ran 39.59) but then I'm better at shorter distances. I did then go and knock a further minute and a bit off that 10k time the following month. I reckon you have a good chance if it all falls into place on the day.

    Stevie – I’m not entirely convinced about the Macmillan bias. What makes you think that? IMO its reasonably accurate overall and I think the times it suggests are good equivalents (i.e. the same standard). Of course the conversion will depend upon what category of runner you fit into and speed/endurance bias. For instance its often the case that for older runners/women it’s easier to hit the longer distance times. But for younger guys who will often have more speed the shorter times are easier to hit than the longer ones.

  • Exiled, my 5k PB was 19:07 when I broke the 40-min barrier earlier this year (39:46), but that was on a pancake flat course on a perfect day for running. Saying that, my HM PB is a few minutes quicker than yours, but if you've been putting in the miles since your half and your endurance has improved you should be ok. If the race in a fortnight is on a fast, flat course, then I'd go for it as you're just about there. Good luck!

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