McMillan calculator times

I've been running again for about 2 months now since being out for a year with 3 consecutive fractures.  I've got my confidence back again which was the hardest thing and am now able to run 8k, I'm building up slower this time. To give me something to aim for I have entered my first marathon next year. It was during my first half mara last year that I fractured my fibula. When training for my half, my 5k PB came down by a minute. I put that PB into the McMillan calculator and was quite surprised by the marathon time it gave me. I just wondered how achievable/realistic this is ? I appreciate that a sensible training plan and remaining injury free are key but should I target this time ? I noticed also that the predicted time for my half was 10 mins quicker than I was aiming for and apart from breaking my leg I was feeling pretty good and considering upping my pace. in the end it was all I could do just to finish !




  • Mr BoatMr Boat ✭✭✭

    I wouldn't be comparing my 5k time to a marathon just yet. What pace were you running your HM at when you became injured? This may be a better guide until you manage to get a few more racing miles under your belt.

  • Absolutely. It's a year away and I have a lot to do before then. I haven't raced a 5k yet but reckon I'm at least 5 mins off my PB time. I was aiming for 1 hour 45 for my HM and was running at about 7 45 m/m at the 7 mile mark and feeling quite good. it was about a half mile later that it went wrong. 


  • The marathon times it gives are wildly optimistic.  Add another five to ten minutes at least.

  • Thanks. If I got within 10 minutes of it I'd still be extremly happy. 

  • literatinliteratin ✭✭✭

    McMillan was actually strangely accurate for my half to full marathon conversion (give or take 10 secs), but there are loads of different factors:

    - HM time is a better comparison because closer in distance.
    - I'm a woman (Fetch calculator reckons that makes a difference).
    - I'm better at long distance than speed, my 5k is (comparatively) pretty crap. This might be why women tend to convert their mara times better than men?
    - I did about twice the mileage for marathon training as I would for a half.

    So what I think is that you can only use the various calculators alongside what you know about yourself and what kind of runner you are (better at speed/endurance, how much time you're willing/able to spend training, etc.)

  • Interestingly the Fetch calculator seems more accurate than the others I have seen.

  • Stevie  GStevie G ✭✭✭

    i know one chap whose 5k and marathon match on the predictor!

    I find that incredible, as I find that from longer distance down, McMillan throws me some outrageous targets.

    Whereas 10miler to half it's pretty spot on.

    I may just be better at long distance, which I don't like the idea of, as those types get sucked into marathons image

  • literatinliteratin ✭✭✭

    Stevie, couldn't you be tempted to just do ONE, just to see...?

  • Just remember the calculator caveat:  time is valid if you've trained for the distance.

    I've comfortably beaten my Macmillan predicted times for everything up to marathon. But not marathon, despite some serious training.

  • Stevie  GStevie G ✭✭✭

    Litty, I covered 26.2miles over 4hours once, which included a 30min drinks and ice lolly break!

    Was a miserable day, boiling hot, and just 2 of us running the route as part of a club "chairman's challenge", which used to get about 20-30people involved, but was dying on it's ass by the end.

    We were meant to do 11miles out and the same back, got the wrong route, and ended up doing the extra 4.

    Despite feeling utterly wiped out, we were bloody minded enough to make up the extra 0.2miles image

  • Stevie  GStevie G ✭✭✭
    Ben Sales wrote (see)

    Just remember the calculator caveat:  time is valid if you've trained for the distance.

    I've comfortably beaten my Macmillan predicted times for everything up to marathon. But not marathon, despite some serious training.

    out of interest Ben, what are your pbs...

    have you tried going down the scale? ie from your half marathon pb, have you beaten what it says for 10k and 5k?

  • literatinliteratin ✭✭✭

    Beating my McMillan 5k and 10k predictions are next on my list. image

    Shit, just realised I'd better not try to beat my half marathon PB till I've done those or it'll get harder.

  • Stevie  GStevie G ✭✭✭

    i can't come close to my 10k off my half time (which was a big pb in Feb)...and can't get to my 5k off my 10k (either the Feb, or March pbs)...and can't get to my 3k off my 5k.

    there's some science in this i'm sure image

  • literatinliteratin ✭✭✭

    ooh, just had a look and my 8k XC time from Jan is pretty close from my marathon time. Maybe I will turn out to be the one example of McMillan calculator accuracy!

  • Talking of Fetch, is it possible to upload my runs from garmin connect?  The Fetch seems to imply that this is possible but doesn't seem to work in real like.

  • literatinliteratin ✭✭✭

    SR, let me know if you manage it, as I want to use Fetch for the analytical tools but haven't been bothered yet rummaging around for details of exactly what gets uploaded and displayed.

  • My 5k, 10k and HM and all pretty much in line. Mara is 20-25 mins too slow on McMillan. That fetch calculator seems better and is only 3.5 mins off. 

  • Lit,  tried again, still doesn't work.



  • SlowkoalaSlowkoala ✭✭✭

    I found the Fetch predictor to be more accurate for my marathon time. If I plug in my half time, it gets my marathon time right within 30 seconds. Interesting that it gives different half to marathon conversions depending on gender.

  • I've just put the same 5k time into the Fetch calculator and it shows a time over 3 minutes quicker than mcmillan for a marathon

  • SlowkoalaSlowkoala ✭✭✭

    Rich, the one I used was the same as Literatin's link. Only gives option of a half time to predict full marathon.

  • Ah OK, didnt follow the link, just went on the Fetch website and used the calculator I found on there.  I've only done the one HM so theres no point in using the time from that.  I guess I'll just work on my 5K time for a bit and get a bit closer to my previous PB and then have a crack at 10K and see if I can get that close to the predicted McMillan time and from there on to HM.  I've got a year so should have time.


  • McMillan gets my marathon/ HM times pretty much bang on. People say its too optimistic over the longer distances but I've not found that to be the case if you put the milage in during training.

  • PhilPubPhilPub ✭✭✭
    literatin wrote (see)


    - I'm a woman (Fetch calculator reckons that makes a difference).


    Now that's interesting, partly because it does differentiate according to gender but also as it's the only one based on actual results that I've seen.  And it predicts my recent conversion to within 25 seconds.  Not bad! (Translation: I must try to get my conversion looking better than average!)

    I think the main reason why formula-based predictors break down at marathon distance compared to the 5k - HM range is the caveat about being adequately trained.  It's pretty much impossible to scale up the type of training you do at shorter distances to the marathon, especially w.r.t. over-distance training, and training at race pace for anything like adequate volume without breaking down. For the race itself, I think there is an additional element of fatigue which means that the pace relationship tails off for virtually all but the best converters.  So it makes sense to have a specific predictor based on real results, and I'll be bookmarking the fetch predictor. image

  • PhilPubPhilPub ✭✭✭

    ...translation #2: I need to learn to run like a girl.  image

  • Just checked out the the Fetch calcuator and its predicting a marathon time 11 minutes slower than I got last weekend from my HM PB. Far too conservative IMHO.

  • literatinliteratin ✭✭✭

    Maybe you run like a girl. Gaz?

  • Apparenty I run even better than a girl!image

  • literatinliteratin ✭✭✭

    I think they've actually changed the Fetch calculator slightly since VLM, Phil, so your and my results will be in there somewhere. Someone on the P&D thread 'helpfully' posted the link to it the day before and I'm pretty sure it was offering me a slower prediction based on my half time than it is now.

    Gaz, I run better than a girl too. image But I suspect it's secret code for 'shit at shorter, speedier stuff'. (me, that is. not you)

  • I agree mate. I've never been sure whether to interpret the results as me having good endurance or poor speed, the old "glass half empty, glass half full" condundrum!

Sign In or Register to comment.