Marathon Predictor Calculators

In the lead up and aftermath of racing a marathon I have been contemplating predictor calculators and why they seem to be off for so many when it comes to the marathon.

A few of my friends insisted I was ready for 3:03 or even sub 3 before Columbus, but in the end I went for 3:05 and obviously that is about where I was. I chose that goal because of my half time at Buckeye Half. In the past my 10k equivalent predictor rate for the marathon was always around 4.78 to 4.83. A comparative 10k time to my 1:26:52 would be around 39 minutes and the ratio for that to my actual marathon time is 4.76. I figured best case scenario would have been just under 3:05 or a 4.75 ratio given my training was more consistent than in the past. But I also know that pacing screwed up a few of my key runs so I didn't want to be too optimistic.

I am wondering what ratio's others have and if you typically set your marathon goals based on your current shorter race performances and if any of the available calculators have been accurate for you.

I find it interesting that all of my races this year except the marathon lined up pretty well in the Daniels VO2 range, but my marathon obviously is not in that same range.

Some tools I have found useful for setting goals and getting an idea of my racing potential:

The old fashioned/simple approach: Half marathon*2 plus 10-12 minutes
Daniels VDOT Calculator:
McMillan Running Calculator:
Race Time Predictor:
Predicting a Marathon Time:

The last link is one I have found intriguing. It bases the predictors on how much mileage you run. I have set up a spreadsheet to track my own personal 10k predictors and actual results along with my mileage. It seems like this time it was pretty accurate. I averaged 62 miles a week for the past 22 weeks or so and my rate ended up being 4.76 (4.78 if you based it off Perfect 10) (Note I just use the McMillan Running Calculator to get an "equivalent" 10k time for my races since I didn't run a 10k this year)

I think I still have a lot to learn about marathoning and I am excited to get faster. But it certainly is intimidating thinking about how fast I am going to need to be in these shorter distance races to achieve my ultimate marathon goals, especially if I need to do even better than most of these calculators suggest!

So my big question for myself is am I limiting myself by setting what appears to be conservative marathon goals according to all these calculators (and personal experience of others) or am I running my best marathons possible by setting a realistic goal. It seems based on my past experience that in order for those online calculators to be more accurate I am going to have to get my mileage up above 80 mpw, a tall order for those of us that aren't cranking out our easy mileage at a good clip.

Feel free to chime in on my rambling here, I am interested in others experience with calculators/goals etc. It's pretty much the down season now, so a great time to consider goals for next year!

*Edited to Add*

For an example case and since it is my blog here are some equivalent 10k times from my races leading up to Columbus and the resulting ratio

Johnnycake 5 Mile- 10k McMillan equivalent and ratio to Columbus Time 39:35/4.70
Perfect 10 Mile- 10k McMillan Equivalent and ratio to Columbus Time 38:52/4.78
Buckeye Half Marathon- 10k McMillan Equivalent and ratio to Columbus Time 39:02/4.76


DaisyDuc said...

Great post as I am really interested in learning more about this too!

KimZepp said...

I would like a calucator that could predict IF I could finish.
Just kidding. Sort of.
Anyhow, this is interesting. I've only run 3 half marys, but I often wonder how I could do / what my time might be if I try the full.

Mark said...

Excellent post! I found the links very interesting! Thanks!

Arcane said...

I like the vdot calculator at since it interpolates between vdot numbers. Sometimes they're accurate, sometimes they're not. For me, i have the opposite problem in that I can't run a 5k or 10k at the predicted times that my half or full times predict. Everyone's different.

Brian said...

I use the predictors to define what my optimal marathon time should be (based on my 5K) and then work that into my training (Yasso's, pace runs, etc). I've yet to nail what most predictors say my optimal marathon should be, but I'll keep trying!

Lloyd said...

For me and the marathon, I've found that the VDOT calculation, plus 5 minutes (my own unscientific method) is a good indicator.

Remember, VDOT is a "comparative performace" chart rather than a "predictor." Consider that along with your training, the conditions, course profile, and other variables of the day ought to be similar as to the event that you plugged into the calendar.

Additionally, the marathon is just different than all of the other distances you might use as a fitness indicator. Marathon requires more tactic and patience, as well as fueling execution. The other distances not so much.

Like Brian, I suggest using the charts or calculators for your training paces. Then on race day go more by feel - at a pace 20-30 seconds above your usual T-pace.

marathon mommy said...

I'm partial to Daniel's. My PRs line up within 1-3 VDOTs of each other even though they've been run over a span of 10 years! The only outliers are ones that I know haven't run a "true" PR. i.e. Half marathon which I've never run all out while in shape.

I know some people swear by Yasso 800s but they were way off for me. They predicted a much faster time that I could have done. My personal opinion is that it may work for beginners or those with not much speed background. Personally, my legs have done countless 400 and 800 repeats over the years (high school and college track) and can crank out much faster 800s than I could the equivalent marathon speed.

Sensationally Red said...

I quit using calculators--they crush my spirit. I never measure up. Heck, I even quit looking at my watch! It was great running with you the other day. Always nice when I can share a short jaunt on one of your easy days. Take care!

Steve Stenzel said...

I never trust pace calculators. In my experience, they always say I can run shorter distances slower than I really can, and longer distances faster than I really can. (But I think that could be an issue with my training, but we'll save that for another day.)

We should talk training sometime. You seem to be running your fast "key" workouts much slower than I do, but in longer races, you're much faster than me. I'm screwing something up. I think I need to run MORE.... ;)