I have only run one marathon (Yorkshire marathon, October 2013) and it was horrible. It was painful both physically and mentally and the most difficult thing I’ve ever done. My next marathon will be Amsterdam.

Before Yorkshire I put in my 10k and half marathon times to many race time predictor websites to get an idea of what time I should be aiming for.

10k baseline time before Yorkshire 00:40:32

Half marathon baseline time before Yorkshire: 01:32:40

Average race predictor website time: 3:08:09

Marathon finishing time: 3:39:52

Sub 3:10 sounded ridiculous for my first marathon so I set a conservative target of 3:30. I was close to this with 3:39:52 but this was nowhere near the 3:08 that was being suggested. I am determined to better 3:39:52 so have entered the Amsterdam marathon to try to achieve this.

After some discussions with more experienced marathoners I was pointed towards this interesting but very long article www.hillrunner.com/jim2/id70.html.

If you don’t want to read it, here are some of the highlights.

  • A race goal that is optimistic, even by just a little bit will probably result in an overly aggressive race plan and a big disappointment in race performance.
  • Predicted marathon times are always optimistic and are based on the runner being “adequately trained”.
  • One reason for optimistic predicted times is because the baseline times are all from shorter less physically and mentally demanding events.
  • Being “adequately trained” often means that you are an advanced, competitive runner who has trained very hard and well to prepare for the target race distance.
  • Calculators may not be using up to date data, so this reduces accuracy.
  • Using a baseline run to predict a marathon time will always be an estimate. Every baseline run distance will be less than a marathon so will not have the same demands as a marathon.
  • The biggest variables in running are lactic threshold, endurance, strength and running economy. All are improved with training.
  • Most predictors simply multiply a shorter race time (e.g. 10k) by a number to estimate a marathon time. The average of several race predictors is a ratio of 4.65. A 45 minute 10k gives 3:29 for a marathon.
  • Doing a baseline run, preferably a 10k or half marathon race, up to four weeks before the marathon will give the best input to working out a predicted time. Doing a baseline run before marathon training starts is likely to give inaccurate results.
  • The shorter the baseline run the less accurate the predicted race time will be. Using a 5k time isn’t as accurate as a 10k time etc.
  • Create your own ratio. Build a data set over several marathon cycles and hone in on an accurate ratio/predicted finishing time.
  • More miles isn’t simply the answer as quality is more important than quantity. For example it’s better to do 30 miles spread over different types of run such as long run, tempo, speed work and have an aim for each rather than 35 miles made up of a five mile jog every day.

One of the main factors that often isn’t taken in to consideration by the predictors is average weekly miles. More training miles will increase lactic threshold, endurance, strength and running economy. Below is a table developed (not by me) to help incorporate the number of training miles.

Weekly mileage Ratio
30-35 5.50
40 5.00 – 5.30
55 4.90
60 4.75 – 4.85
70 4.70 – 4.80
80-100 4.55 – 4.65

Looking at multiple predictors, the average ratio is 4.65. Using table above the average ratio is 5.

My average weekly miles in the build up to the Yorkshire marathon was 28.6. I had a 10k baseline time of 40:32. Using the above table and a ratio of 5.5 it predicts a marathon finishing time of 3:43. My actual finishing time was 3:39:52. Using multiple website my predicted time was 3:08.

Creating your own personal ratio will take some time so in the meantime, here is a sensible approach.

Run a 10k race 3-4 weeks before a marathon. Use both a race calculator and the table above to predict marathon times. Then, base your marathon goal and race plan on the slower of the two methods. Remember, a little conservatism is better than being overly aggressive.

Based on the fact that the predicted time was so close to my actual time, I think this approach is brilliant.

These are just thoughts and ideas. Some are my own and some are taken from the link above.

I hope this helps.