Marathon sub-x times equivalent in FTP xW/Kg

I had that rare luxury of time on my hands tonight, and found myself wondering what would be the ‘equivalent’ FTP W/kg ratio to, say, a sub-4 or sub-3 marathon runner?

Would a 3W/Kg person in the cycling world be the equivalent of a sub-4 person in the running world, for example?

Would say 3W/kg and sub 4 hour marathon runs are pretty equivalent. It’s a level that most healthy people under 40 can get to with training. 4W/kg is maybe equivalent to sub 3 in marathon. Starting to get to the pointy end of things, requires some fairly serious training commitment to get there unless you’re blessed with a lot of natural talent, you’re faster than 90% of runners/cyclists out there but you still get blown away by the real top end athletes.

Would also say that generally a lot of people can achieve a higher percentage of their potential in cycling than running because of running being an impact sport. Being able to handle a high volume of running training without breaking down or getting injured is a talent in itself.


I agree with 3w/kg being a similar milestone to a 4hr marathon but I think 4w/kg is closer to 3:15 perhaps.

For someone who is healthy, in their 30s and follows a plan consistently I feel like 4w/kg is achievable for a fair proportion. I don’t think a sub 3hr marathon is possible for most people off an equivant amount / duration of training.

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(disclaimer, if we use pure crude averages in conjunction with some fuzzy math from Coggan for 4w/kg and the various calculators and completely ignoring that cycling and running produce different VO2max values, I am not a scientist yada yada yada)


  • 5w/kg = ~75 VO2max ml/min/kg
  • 4w/kg = ~60 VO2max ml/min/kg
  • 3w/kg = ~45 VO2max ml/min/kg


  • 75 VO2max = ~2:15 marathon
  • 60 VO2max = ~2:45 marathon
  • 45 VO2max = ~3:30 marathon

This also assumes that your state of training between the two sports is roughly equal. There is no way I could go out and run a 2:15 marathon, but that probably represents a long term goal if I were to start running and commit for many years.


I’m currently riding at 4W/kg and last year ran 2:51 and had a VO2 of 66 when measured 5 years ago (aged 41) so the n=1 assumption holds true.

I would say that getting to sub 2:50 shape (I was disappointed with not getting 2:48) was way harder on the body than getting to 4W/kg


I’d imagine this to be the case. Running has a big durability and efficiency element to consider. I was a good mile to 5k runner as a teenager, but unfortunately born with a big engine but terrible biomechanics. Messed up my lower legs royally and called it quits.

At 39 with 18mos of training I’m around 5wkg and pretty good numbers from 1min to 4+hrs. I’ve done some cycling and a bit of racing in the past, but just a year or two here and there. First time training with power or any structure. Cycling let’s me make the most of my engine with limited stress on the body. Managed around 600hrs last year and aiming for similar in 2020.

Point being, I’ve banged out some random 5k in good times over the years but to train for a 2:15 marathon would break me, literally.


Now that’s another interesting statistic to look at, 12 hours a week to 5W/kg. I’d say that’s pretty damn good :muscle::+1:

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That’s really interesting! at 4.3w/kg and with a v02max of 60 I don’t think I could run a 2:45 marathon in the near future…maybe sub 3? (and I’m generally a more competitive runner than I am a cyclist)
I wonder if these kinds of predictions would differ for females. I think a lot of my w/kg ratio is based on me being pretty small as well, and in my experience lighter people don’t tend to hold up as well on races of marathon length and above.

I used to be a sub 3 marathoner, got down to sub 2:50. I was strictly running though. I’ve been as high as 3.5w/kg, but I’ve never fully committed to cycling so not sure how high I could get. Now I just split time as I want. I’m a little older now, too. I don’t think I could run sub 2:50 anymore without serious, serious work.

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What was your fastest 5k or 10k time?

I ran 34:15 four weeks before my 2:51, which as a 45 year old is perhaps more of an achievement

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If you want to look at the other end of the spectrum, I’m around 2,5W/kg FTP, and a 1:53 half-marathon runner; VO2Max last tested at 42 (although Garmin insists on telling me I’m at 48 and could run a 1:39 half) That also confirms the table above is a bit on the enthusiastic side.

Indeed - the last time I did a 10 below 40mins, I was a lot younger than 45 (and even more than my current age).

Thanks for the replies. It seems like we all have ideas of equivalents in and around the same ballpark.

Last year I did a pb of 2.39 and got up to 4.5W/kg. A sub 3 marathoner can always place reasonably well on any running course, but even at over 4.5W/Kg I don’t feel like my raw Watts are enough for flatter races.
I’d love to crack 2.35 next year and try to get back to 4.5W/kg, before my body starts rebelling (I’m 42)

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FWIW, I’d guess the equivalent for 5W/Kg is closer to 2:20-24 ish. As a runner, I’ve run 4’19(mile), 25’10 (8k XC), 31’45 (10k XC). Never actually trained specifically for a marathon, but I’d probably aim to crack 2’30 when I do. As for cycling, never actually trained for it outside of just riding. The two times I did a ramp test I was just over 4 W/kg coming in “raw”.

Wouldn’t a 10KM or 5KM be more representative here

If it’s about threshold, running threshold is more around 5KM pace surely?

It would probably be closer to 10 mile. Most of the top elite males are going to run sub-55 down to somewhere in the 40’s. So it starts getting closer to that hour range. 5K is going to be closer to that 15-18 minutes which is a lot different than a FTP predicting for an hour.

I’d agree with most replies here, I think the biggest hurdle for comparing the two is the endurance factor. Going sub 3 requires some serious running mileage while we can reach 4w/kg without really going long.

To add to the collection of anecdotal data here, I’m usually peaking my tri season barely clearing the 4w/kg threshold and running 17:50 / 37:10 / 1:25 for the 5k, 10k and half marathon. Haven’t run a full in anger for a while but I’d have a hard time going sub 3 lacking the mileage and long runs.

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