Marathon Training: How Long Should Your Longest Long Run Be?

The long run is the hallmark of a marathon training plan. It is the most important training run for marathoners in their training block, ending with the longest long run. 

The longest long run caps a marathon training block and marks the end of rigorous training in favor of a marathon taper which allows for the body to recover and prepare for race day. 

Many runners stress about the longest long run, confused as to how long the longest long run should be. 

Some training philosophies say your longest long run should be focused on time. Some say you should focus on mileage. Some say your long run is determined by your overall weekly volume. Some plans even have runners running the full 26 miles in their longest long run.

How long your longest long run should be is not a straightforward answer. As with most training for runners, it depends on a lot of factors. 

Related: The Marathon Long Run Training Guide

In this article, we are going to help you determine how long your longest long run should be. We will break down:

  • The purpose of the long run
  • How and how often to run a long run
  • When and how long your longest long run should be
  • How to estimate your marathon finish time
  • Factors determining your longest long run time
  • Should you ever run 26 miles before a marathon
  • The shortest and longest long run you can do in marathon training

So, let’s get going!

Marathon Training How Long Should Your Longest Long Run Be

What is the purpose of the marathon training long run?

The long run helps a runner prepare mentally and physically for the marathon. 

A long run spurs physiological changes in the body including building mitochondria and capillary density; increasing VO2 max and blood volume; strengthening tendons, muscles, and bones; optimizing energy pathways; and improving neuromuscular fitness. 

A long run also helps build mental toughness and confidence in a runner, teaching them that they can do it! 

It’s also an opportunity to practice what to wear and fueling and hydration strategies that can make or break a marathon!

Related: What to Eat Before a Long Run

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How do I run a long run?

The majority of the distance of your long run should be done at an easy pace which is the optimal zone the physiological changes take place. Plus, it allows you to recover and be able to do the next run without risk of injury

Related: How You’re Screwing up Your Long Runs

As you progress your training, it’s possible you will have some marathon pace miles or fast finishes in your long run to build endurance and speed. That should be stipulated by your training plan or running coach. 

Related:  Fast Finish Long Runs: Endurance Meets Speed

How often should you do a long run?

Most long runs are done once a week. 

Some plans may do a long run one week, a shorter long run the following week, before elongating the long run by a mile or two the following week. 

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More advanced marathon training plans may have a mid-week long run that is about 90 minutes to 2 hours long, plus a longer long run on the weekends. 

Every training plan should include a reduction in total volume with a shorter long run every three to four weeks to absorb the training load and prevent running injuries and burnout. This is often called a cutback week or down week. 

Related: 8 Long Run Variations to Build Endurance

When should you do your longest long run?

The longest long run in marathon training is most often done about 3 weeks out from your marathon. 

The timing largely depends on how long your marathon taper. If your marathon taper is two weeks or four weeks long, your long run will then be two weeks or four weeks out from your marathon. 

The longest long run marks the beginning of your marathon taper in which the body recovers from your progressive training load and gets ready for race day.

See also: 11 Tips To Nail Your Long Run On A Treadmill

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How long should your longest long run be?

In general, your longest long run should be at least 2 hours long and no longer than 4 hours.

The duration of your longest long run of marathon training depends in large part on what your estimated marathon finish time will be. This is because you need to teach your body how to run for that duration while not overstressing it so that it’s fully recovered by race day.  

Here are estimated durations according to Norris and renowned running coach Greg McMillan of what your longest long run should be based on estimated finish times:

  • If your marathon finish time is below 3 hours, then you will likely do 1-3 long runs of about 3 hours, or no longer than your estimated finish time.
  • If your marathon finish time is below 4 hours, you will likely run 1-3 long runs of 3:30, (over 20 miles), and (again) no longer than your estimated finish time.  
  • If your marathon finish time is above 4 hours, you will cap your long runs at about 3:30 hours.
  • If your marathon finish time is about 5 hours, you will cap your long runs to 4 hours. 
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In most cases, your long run will be no more than 30 to 35 percent of your overall weekly volume. Therefore, if you run 50 miles a week, your long run will be about 17 miles. 

There are many caveats as every runner is different. 

One big caveat here is for low mileage runners averaging less than 35 miles per week. Their long runs may be up to 45 percent of their total weekly volume, says Norris.

Low mileage runners and/or runners who run a 5+ hour marathon time need to prepare their bodies for the duration of time on their feet. This is why they will run for more time in their longest long run. 

How do I estimate my marathon finish time?

You can estimate your finish time by taking another race time or time trial and using famed running coach Jack Daniels’ VDOT calculator to estimate your marathon time. 

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What factors determine your longest long run?

There are three main factors that determine how long your longest long run will be:

  • Estimated finish time
  • Injury risk
  • Running background

Estimated marathon finish time: You can’t say every marathon plan should include a 20-mile run because a 20-mile run will be much less taxing on a 3-hour marathoner than it would be on a 6-hour marathoner, who will likely take twice as long to complete the distance.

Thus, it’s important to think about your longest long run in terms of time on your feet. 

Injury risk: If the repetitive impact of long runs puts a runner at risk for injury, then the runner should cap the length of their long runs. If long runs leave you feeling sore and exhausted for several days, tune into what helps you recover better and leave yourself extra time to recover, e.g. do a training plan that steps up the long run every 2 weeks. 

Background: If a runner is used to doing long runs or high mileage, then they can likely handle longer long runs. However, if a runner is a new runner, gets injured frequently, or is used to running shorter distances, then cap the longest long run in favor of the runner’s health. 

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Should you ever run 26 miles before a marathon?

You should not run 26 miles before a marathon.

If you run 26 miles before a marathon, you put your body at risk for injury and poor performance since you will likely not be recovered by race day. 

What is the shortest long run you can do in marathon training?

The shortest long run you can do in marathon training is 16 miles. The duration for how long this will take a runner will vary widely depending on the pace. 

“Very few marathoners (i.e. elites) will go under 2.5-3 hours in training. At this duration, you maximize the biomechanical and metabolic stressors of a long run,” says Norris.

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What is the longest long run you can do in marathon training?

The longest long run faster runners will do is most commonly around 20 miles, though, some may run up to 24 miles. 

The duration of a long run is capped at 4 hours because the recovery becomes too significant past this point, says Norris. 

“Too long of a long run means you may be more likely to skip following training sessions. Or you may find that you aren’t recovered by race day and left your race in your training,” she warns. 

Remember: Training is not about one single run. It’s about the accumulation of your hard work over several months! 

Nail your longest long run with Marathon Handbook’s marathon training resources!

Photo of author
Whitney Heins is the founder of The Mother Runners and a VDOT-O2 certified running coach. She lives in Knoxville, TN with her two crazy, beautiful kids, pups, and husband. She is currently training to qualify for the 2024 US Olympic Trials marathon.

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