I’m a big believer in trusting in your training, put in the hard work and you’ll be rewarded. I have said it many times on this blog running is an honest sport, this of course is a two edged sword with very few examples of running faster than expected times off poor or no training. Of course returning from injury can sometimes be a blessing in disguise because you are forced to take some time off and this, combined with good training before and after the injury, can surprise you with better than expected times. Which leads me to the point of this post, predicted finishing times for longer races from shorter races.  The main example I use is my current half time times two and add 10 minutes, this  will normally be pretty close to my marathon time. e.g. if I’m running 1:20 for the half my marathon time is around 2:50 (1:20 * 2 + 10 minutes)

My current half PB is 1:15:00 but this hasn’t translated to a 2:40 marathon ( I managed 2:41:41 ) mainly due to the half time being one of those races when ‘the magic happens‘ and you out perform what you thought you were capable of. Saying that to get to within 2 minutes is pretty accurate. When I ran my marathon PB , 2:41:14 my half time was 1:16:24 which was closer. You can use a 10k or even a 5k time as an indicator but of curse the margin for error is probably larger as you are multiplying the finishing time by either 4 (10k) or 8 (5k). There are various websites where you can ply in your predictor race and your goal race and get an estimated finish time.  A good example is the McMillan website ( https://www.mcmillanrunning.com ) or Runners World ( https://www.runnersworld.com/marathon-training/heres-a-better-marathon-time-predictor )

The Runners World race time predictor has bee rebuilt apparently (see below)  It seems most race predictors are overall generous with their predictions and the work by Andrew Vickers paints a gloomier picture by also adding in weekly mileage. Common sense really as those runners running higher mileage would be better prepared , cardio-wise if nothing else, for the longer races. Most, if not all, race predictors never ask for weekly training mileage, strange this has been over looked.

As always I have an amusing story reference race predictors. My good friend Mike Kowal wasn’t running as much as he should have been due to injury (we use to call him ‘sick note’ as he was injured so much. There was the amusing story where he got injured at the sports massage clinic because the physio left the heat pack on and told Mike to call out if it got to hot. Not wanting to seem a wimp Mike kept quiet and ended up with second degree burns ! You get the picture…)  Anyhow because Mike hadn’t run a half , 10k or even a 5k he started to predict his marathon finishing times off even shorter distances, At one point I’m sure he had it down to a 10 metre sprint. This is not to be recommend for predicting a marathon finish not matter what magic he used, it is to be noted Mike is an Engineer and probably developed some devilish formula to show a sub3 prediction of a 4 paces sprint. Funnily enough he did go sub3 on his first marathon but has yet to repeat the magic on subsequent outings.

All joking aside can you use a race predictor and rely on the predicted time to set your pace for a marathon ? Remember the marathon runner who slows the least normally wins (or achieves their goal). Predicted time and the resulting race pace is pivotal to success when it comes to running a marathon so get the predicted time wrong and the race pace will also be wrong,  which equates to failure. I like the idea of entering two previous results in the Runners World predictor because it adds in experience which is so important to race finish times. I can predict to within +/- 90 seconds my marathon time these days and this is all down to experience. With over 60 marathons and ultra’s under my belt I can predict my race pace very accurately and have only hit the wall twice, once in my first marathon by not preparing and running a time beyond me and once when I was struggling mentally and talked myself into failure. (I have covered the mental part of marathon running in various posts, so important and so under estimated.) With experience and good quality training comes consistency. 

I used the Running World Race Time Predictor and added in my best 10k and 5k times and adjusted the weekly mileage until I got a sub 2:40 marathon time. I had to get two 160 km a week (100 miles) to get my predicted time under 2hrs 40 minutes for the full marathon. Probably about right truth be told but it never asked for my age which would surely be another factor that would be pivotal to the accuracy ? I’m 51 in a few weeks and assuming all the variables where the same I would expect a 35 year old runner, for example, with the same race times  to out perform me. Maybe I’ll try and run a 2:38:30 in June this year, hell the computer says ‘Yes’ so what could possibly go wrong ?

Runner’s World has updated its Race Time Predictor to give you a more accurate assessment of your likely marathon finish time. What’s changed? For starters, when predicting a marathon time, you can now input the results of two races you recently completed, instead of just one. Because past finishing times are helpful in determining future finishing times, this info will produce a more accurate result. In addition, the new Predictor allows you to get a result adjusted for your average weekly training miles. If you ran 50 miles a week in training, you will get a faster predicted time than if you ran 20 miles a week. This is a breakthrough approach not available from other calculators.

The new Predictor is derived from data-driven research just published at Bio Med Central. The paper, titled “An empirical study of race times in recreational endurance runners,” is available as free, full text. Lead author Andrew Vickers, a sub-3-hour marathoner and cancer statistician at Memorial Sloan Kettering Cancer Center, found that most pace calculators underestimate correct marathon finish times by 5 to 20 minutes. As a result, runners using the calculators to pace themselves might start too fast in their marathons—a sure recipe for failure.

A smarter method: Have a more accurate appraisal of your marathon time from the start, and plan your pace accordingly. That’s what the new Predictor is designed to help you do. (Keep in mind predictions can be moot without the right plan to get you to the starting line. Find the perfect Runner’s World training plan for your goal right here.)

Many previous online calculators are based on innovative work done by American runner and course-measurement expert Pete Riegel. Only Riegel faced a severe limitation: When he created his first “equivalent time calculator” in 1977, he had little data to work with, so he based his calculator on the performances of world-record holders, fully realizing that his formula might not apply to mid-pack and back-of-the-pack runners.

Once unleashed, Riegel’s formula became so popular that it took on a life on its own. Many websites adopted it, while few questioned its limitations.

Other calculators were based on aerobic fitness, a key component of marathon success, but far from the only one. (See more below.)

To devise a calculator based on the performances of more typical runners (non world-record-holders), Vickers collected training and race-results data via web survey from 1,022 recreational marathoners. His subjects had an average marathon finish time of 3:28 (men) and 3:54 (women), roughly 50 minutes faster than average national times collected by Running USA, but still far from elite status. And, the Vickers data set included 150 runners with marathon times over 4:30. “That’s a reasonably large number for statistical analysis,” he says, “and much larger than many other studies.”

When Vickers ran the numbers, he discovered a discrepancy between his results and other marathon predictors. Here’s an example: Let’s assume you have run a half marathon in 2 hours and want to estimate your marathon time. While many online calculators will give you a prediction from 4:07 to 4:12, Vickers finds that 4:17 to 4:30 is more accurate.

Runner’s World continues to use the Riegel formula for race time predictions up through the half marathon. Both Vickers and others have found that it works well for 5Ks, 10Ks, and half marathons—all the common distances shorter than the marathon.

When it comes to the marathon, however, many factors beyond pure aerobic fitness come into play. These include: training volume, fueling (pre-marathon and during-the-marathon), hydration, thermoregulation, and more. All these factors tend to slow your marathon pace, which is exactly what Vickers found in his data analysis.

Because of this, the Runner’s World Race Time Predictor was rebuilt to incorporate the more accurate formula developed by Vickers when predicting marathon times.

Of course, a lot depends on your training mileage. And the Vickers formula, unlike the others, allows you to input your weekly mileage along with your prior race times. You won’t be surprised to learn that the more you train, the faster your predicted marathon time. (Not only does it allow for training mileage, it actually requires it. So, if training mileage isn’t included, the Predictor falls back to the Riegel formula.)

Vickers’s analysis also reached other potentially useful conclusions counter to conventional wisdom. These include:

• Training mileage affects all race results equally. In other words, your training mileage is just as important for 5Ks as it is for marathons.
• Tempo training has a greater impact, correlating with faster times, on 5K and 10K race results than on marathon results. Also, tempo training is slightly more effective in general than interval training. Interval training has the same impact on all race results; it’s not more important for the 5K and 10K than it is for the marathon.
• Aging affects all distances equally. It doesn’t have more impact on shorter distances than on longer distances.

And, in support of conventional wisdom, Vickers found that women come closer to men in the marathon (running about 10 percent slower) than in the 5K (about 20 percent slower). And, of course, more training miles lead to faster race results for everyone. Check out the new Runner’s World Race Time Predictor.