Ultrarunning: Training Guidelines for a 100k

August 1, 2011

This article is part of Endurance Planet’s ultrarunning article series. If you have questions, comments or feedback about “Training Guidelines for a 100k”, please leave it below in the comments section…

Among the various ultramarathons, the 100k is perhaps one of the more popular types. Around 200 races of this distance are organized annually across the globe. They could be on tracks, road loops, or trails through diverse kinds of terrain. Along with the 50 miler, the 100k is a common first attempt at ultrarunning for those fairly new to the sport. So here are some training guidelines that veterans and experts typically say will help you prepare to run a 100 kilometer race.

Training focus

If you’ve run standard marathons before then you’ve already established your weekly mileage for such races. But that’s likely not going to be enough.

Doing at least 40 miles a week is what’s considered to be a good base for the 100k. Then as the year of training progresses, try to push it up to 60 miles and more. In this way your body gets used to the considerably longer distance and come race day, you’ll feel more comfortable and confident.

Long runs will be an indispensible part of your training and they will have to be done much slower than your marathon pace.

Time goals

Perhaps due to its popularity, the 100k tends to be quite competitive and a lot of runners seek to complete the distance in less than 10 hours. To get a rough estimate or prediction of your 100k time, multiply your average marathon time by 2.8. This is assuming that you’re in top form and nothing untoward happens during the race.

Yes you’re going to be running slower compared to a marathon but with a set time goal, you also need to focus on establishing the right pace. If you want to achieve sub 8:30 for example, then you’ll have to go at a rate of 8 minutes per mile or slightly faster. So besides the all-important long run, you’re also going to incorporate some fast running. That means doing some fartleks, tempo running, or uphill workouts.


You may have read or heard how some runners join smaller or shorter events as a way to prepare for the actual race they’re targeting. This is a legitimate way to train and gain the necessary experience. But before you go ahead with this approach, be careful not to disregard tapering.

One suggestion is to join a 50k race about two months before the 100k event in order to evaluate your overall condition. Then sneak in a 10k half-marathon or two in between to see how you do in terms of speed. Leave a 2-3 week taper prior to the target event.

There are a lot of online resources that outline workable training schedules. Just be sure to adapt them to your specific needs and limitations. If you’re going to do long runs in the weekend for example, then place your speed training or pace work somewhere mid-week.


If this is going to be your first 100k or even your first venture into the world of ultramarathons, then you can only increase your chances for success by getting yourself a coach. Remember that ultras are a completely different animal to standard marathons. It’s better to have someone with the right credentials and experience to be there guiding you during your preparations. You can always try local marathon or track athletics associations in your search for coaches who specialize in ultrarunning.


Do you have questions about training for a 100k, or what you’ve read so far? Do you have any ultrarunning pointers of your own to add? Please leave your feedback, comments and questions below, and we promise we’ll respond.

Comments (5)

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  • Good article, I would have liked to see more information on the breakdown of long run distances and pacing within the mileage increase from 40 to 60 miles per week.

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  • jasonmellet says:

    Um…multiply your marathon time x 2.8…where did you guys come up with that BS for a prediction of your 100k time??? holy crap..

    I run about a 3:30 marathon..by that thinking i should of finished my 100k this past weekend in 9 hours…um..hello i did it in 15:04 ( which was the winning time )

    ive never heard of anyone finishing a 100k in less that 10 hours unless they were elites OR it was on the road. 100k's are seldom on the road and its seldom about speed, especially because its on trails and have tons of elevation and technical trail.

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