How To Pace A Marathon

Essential guide to accurately predicting your marathon finish time and creating your race plan.

If you’re running a marathon, it’s vital that you predict your marathon race pace in advance. Then you can formulate a realistic pacing strategy that will maximise your chances of success.

It is no coincidence that the vast majority of marathon runners complete the second half of their race significantly slower than the first. This is often because they set themselves unrealistic pace expectations, based on a combination of past performances and blind hope. Over such a long event, any misjudgments in pace can have big repercussions later on in your race.  Predicting your marathon race pace accurately has several benefits:

⁃    Faster race times
⁃    Quicker post-race recovery time
⁃    Increased morale (as you overtake runners in the second half)
⁃    Greater satisfaction during and after the race

Predict Your Marathon Time

There are various ways to estimate your marathon finish time and race-pace, including online calculators based on your result from a previous race. These predictions often use the Riegel Formula – a basic formula published by Pete Riegel in 1977 that can be used for all distances, from 5km to marathon.

The Riegel Formula: T2 = T1 x (D2/D1)1.06

D1 = the distance you’ve already run
T1 = the time it took you
D2 = the distance you’re about to run
T2 = the predicted time.

The Riegel Formula is a useful predictor, particularly for shorter races, but less accurate for long races such as marathons. For example, a 1:45 half marathon would give you a predicted time of 3:38 for a marathon. That’s doubling your distance and adding only eight more minutes. For most runners, that’s unrealistic.

Thankfully there are two better methods.

1. Ian Williams Method

The creator of this calculator, Ian Williams, studied a database of 30,000 marathon and 57,000 half marathon performances to improve the Riegel Formula. His research highlighted a discrepancy between men’s and women’s marathon results, showing that women run at a slightly higher percentage of their half marathon race-pace during a full marathon. Which means that this marathon predictor is gender-specific, as well as being based on a large number of race performances.

2. Marathon Time Predictor

This online calculator is based on a study “An empirical study of race times in recreational endurance runners”. This study looked at the Riegel Formula and the factors that correlate with marathon finish times, to give a more accurate method of prediction.

The main advantage of this marathon race predictor is that it is based on several variables. You can enter the results of two races you’ve completed, instead of just one. And it asks you for your average weekly training mileage. The higher your mileage, the faster your predicted time.

What To Do With Your Predicted Marathon Times

Use both of the above calculators to get a good idea of your predicted marathon finishing time. You can then do a Google search for an online running pace chart such as to show your average pace in minutes per mile or minutes per km. You should then aim to maintain this pace throughout your marathon, allowing for a small margin of difference for subtle variations in gradient and wind.

Other Things To Consider

Once you’ve calculated your predicted marathon pace, there are a few more variables to consider.

If your marathon is to be done in extreme weather or over challenging terrain, your predicted times will not be so accurate. In fact, using pace as a guide over hilly routes or in extreme winds is a bad idea anyway, because there are too many variables. You wouldn’t expect to run at your normal marathon pace, up a steep hill for instance. In this case Heart Rate or Rate of Perceived Exertion are more useful guides to intensity.

Similarly, if you enter a half marathon finish time from a hilly race into the marathon predictor, it will spew out a marathon prediction based on a hilly route. So make sure you use recent races that are similar (for example, flat and fast) to the marathon you’re aiming to predict.

Lastly, if you’re looking to predict your finish times for a 5k, 10k or half marathon, you can use our own online race prediction calculator.

Are you a beginner, intermediate or advanced amateur marathon runner?  Do you want help with your training? Preview our Training Peaks marathon training plans or feel free to contact us. You will also benefit from email coach access, with prices starting from just $29 USD. ​

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Phil Mosley (Coach & Founder)
Phil Mosley (Coach & Founder)

Phil is a recognised expert in the field, having featured on many endurance sports publications. He founded MyProCoach in 2010 to sell premium training plans complete with email coach support for triathlons, duathlons, running & cycling.

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About Phil Mosley

About Phil Mosley

Phil is a successful coach & athlete, having sold over 20,000 training plans on TrainingPeaks and been featured on countless publications. His focus is on smart training that still leaves quality time for your family, friends & career. You can learn more about MyProCoach™ here or preview your training plan now.

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