Fit Fanatic: The McMillan Running Calculator

By Cool J in Minneapolis

In my post on the Securian Winter Run, I mentioned the McMillan Running Calculator

http://www.mcmillanrunning.com

After that post, we received a nice message via facebook from a reader. (FYI, be sure to “like” The Right Fits on Facebook, and we welcome comments and messages!) The reader asked us about this calculator and whether we feel that it’s accurate.

The McMillan running calculator is one of many that exist, though generally this seems to be considered one of the “best” ones.

This calculator doesn’t just double your time from a half-marathon, and assume that’s your full marathon time. Instead, it uses years of history from runners and race data to help determine training paces and races paces. To be honest, when I first started long-distance running, I thought I could just double my time; I thought if I could run a 2 hour half marathon, that meant I was on track to run a 4 hour full marathon.

But unfortunately, that’s not true. Your half marathon race pace should be significantly faster than your full marathon pace. According to the McMillan calculator, a 2 hour half marathon (9:10 min/mile pace) should indicate that you’d be able to run a 4:15 full marathon (9:38 min/mile pace).

But there are no true predictors of your full marathon time. There are so many factors that go into each race- the weather, how rested you are, the course, your mental state, what you ate the days before, how your training went, etc. etc. However, I do think that these types of calculators are helpful for training. They are helpful for setting personal goals, and reassessing them if necessary. For example, I know that my goal for a half marathon is 1:46 (8:10 min/mile), knowing that my goal for a full marathon is 3:45 (8:35 min/mile).

But if my next half marathon day is extremely hot, or I am recovering from a cold that day, or I just have a bad day, and end up with a 1:55 time, does that mean my goal of 3:45 in Newport is no longer achievable? Of course not.  Again, these calculators are training tools, not psychics!

In my limited research, I came across this forum on Runner’s World with lots of discussions on success stories with this calculator:
http://forums.runnersworld.com/forums/training/5k-10k-half-marathon-race-training/re-mcmillan-running-calculator-success-stories

One commentor provided these caveats for using the McMillan calculator:
1 – The closer in length the “predicted” race is to the “predictor” race, the better the accuracy of the McMillan prediction. (A 5K time predicts an 8K time better than a 5K time predicts a half marathon or marathon time.)

2 – The closer in time the “predicted” race to the “predictor” race, the better the accuracy. (A January 2012 race time predicts a February 2012 time better than January 2006 race time would.)

3 – If you are stepping way up in distance, you have to modify your training so that what you do for the “predicted” race is as appropriate as what you did for the “predictor” race. For instance, you might have run fast 5K off 30 quality miles a week. That won’t, however, produce the fast marathon your 5K time predicts without a big bump in mileage and deemphasis of speed work.

4 – It helps to know yourself. You may have greater physical/psychological aptitude for races at the short (or long) end of the spectrum. 

How does McMillan’s calculator work? 
I wasn’t really sure, but I found this explanation on Runner’s World’s website:

“All the running calculators use the same basic relational associations between various race distances and between race performances and training paces. McMillan hasn’t “discovered” anything new. However, he did quantify training pace ranges, as opposed to single training paces as most of the others do. I like the approach of pace ranges because not every training day is the same as all others.

All of the race “predictors” are reasonably accurate for distances up to half marathon, as long as one trains properly for the distance being “predicted”. Where many people have difficulty achieving the predicted time is in the marathon. Many, if not most, fall short of the prediction due to inadequate training base (mileage) or poor race execution (bad race pacing).The “secret” to achieving race time predictions isn’t so much in the training paces specified by a calculator as in the balance and appropriateness of the composite training program one is using for the distance for which one is training.”

So, it’s true that even if I can achieve a 1:46 half marathon, I may not be able to do a 3:45 full marathon. But it does help me to have that goal in mind for the shorter distance races, and to have an idea of just how hard to push myself. Even if the calculator isn’t perfect, it does offer some insight of value.

McMillan’s website also offers a paid service with recommended workouts, heat adjusted calculators (this would have been super helpful at the Iowa marathon which was in the 90s…)

Check out this video from the McMillan website for more information on their customized training programs.