Race Time Predictors

Am interested if race time predictors work for you as on www.runningforfitness.org .

I plugged in my time for 5K and it predicted I should be able to do a 10K about 3 mins faster than I have managed. In fact the longer the distance the more its out.


  • What was your 5k time and what prediction did it give for 10k?

    Predictions are generally for the best you could do, based on the best you have done, and achieving your best when racing is the exception not the rule.

  • Hmmm, I only wish this were true;

    10k time is 47 mins.  From this it predicts;

    1/2 marathon of 1.43 (managed a 1.49)

    Marathon of 3.34 (in my dreams, only ever hover around the 4 hour mark...that's a big difference!)

  • H.

    The time prediction formula I use (from old RW mag) predicts 1h 46 for a half, and 3h 46mins for a full based on 47 for 10k.

    Plus to achieve your best possible times you need to have everything go right for you, (your condition, the course, the weather) and that so rarely happens in longer races (not too often in the shorter ones either)

  • For me the various predictors work best when predicting races which are not too far apart in length (5k to 10k; 10k to 1/2M).

    For predicting marathon times I have found that my actual times (for 2 marathons) are slower than predicted (which I am not surprised at). Many online predictors calculate marathon time as 10K time multiplied by approx. 4.7 (sometimes less). However I suspect that such ratios are based on times for elite runners, and/or runners who were achieving high weekly mileages.

    I read an article, which linked marathon times to average weekly mileage during the marathon training programme. For example, it suggested that an average of 40mpw would result in a marathon time of 10K time multiplied by 5 to 5.3.

    While it didn't comment on factors such as whether a runner was attempting a first marathon, or their ninth or tenth, I suspect that cumulative mileage over a number of years also has an influence (I certainly hope so).

  • I understand what you mean Big David....but

     I ran a 5K in 19:30 mins and best for a 10K is 43 Mins. I know I tried pretty hard but simply was not fit or strong enough, I think, to do a predicted time of less than 41 mins.

    An element of strength or stamina  must come in to play for longer races??? 

  • Close - I have a marathon PB of 3:48 and on that day I passed through the half at 1:47 and 25km at 2:09, which was also a PB. I think it works better for longer distances - I've done sub 4 mins for 1 km, 23 mins for 5km but never dipped under 48 for 10km. I can run fast for short distances but have a great deal more strength and stamina than speed so do rather better on longer courses.  As others have said, the other variables such as training, running history, weather, health, play a big part.
  • Hi Full Up.

    My prediction for 10k based on 19.5 for 5k is 41.5, not sub 41.

    But you are right. If you haven't built up the stamina required for a distance, you will struggle to complete the distance, let alone achieve your predicted pace.

  • Thanks - got the message - simply have to train for the distance and if everything else is right then should get the predicted time.

     I think Big D's predictor (formula) is more accurate.....has it got a name?

     [Its higher than age grading, vo2 max, purdy, Riegel and Cameron formulas]

     Is there a way to measure stamina?

  • The formula is T2 =T1 x (D2/D1)^1.09


    • D1 is the distance you have raced in miles eg 10k is 6.2
    • T1 is the time it took in minutes eg 52min 54secs is 52.9
    • D2 is the distance you are aiming to do half mara is 13.1
    • T2 is the predicted time in minutes 119.6 (1hour 59mins 36secs)

    If it has a name I don't know what it is.

    And I have seen the same thing with the power 1.09 replaced by 1.07 and even 1.06.

    In the example above 1.07 would give 117.8 & 1.06 would give 116.9.

  • I think they're best if you use all of them and then take an average. I recently checked my times on 5 or 6 of them as I wanted to know if a target of a 3:30 marathon was reasonable. Their marathon estimates ranged between 3:12 and 3:28 using the same 5k, 5 mile, 10k & 10 mile times. My conclusion was that my target is not a complete dream, but I doubt I'll look at them again.

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