The long run is the backbone of marathon training. It’s the workout where you build the aerobic endurance and durability needed to conquer the final miles of your race. It also allows you to practice the fueling strategy and pacing discipline that’s required for conquering the full 26.2.
But when you’re staring at your marathon training plan—and trying to fit those miles in around your already overwhelming schedule—it’s fair to wonder how short your long run can stretch without thwarting development and undermining the rest of your training.
According to coaches, your minimum long run mileage for a marathon depends on a number of factors, including your current fitness level, pace goal, and injury history. After all, a first-time marathoner trying to finish 26.2 safely will not use the same long run progression as an advanced runner trying to break 2:30. Still, there are baseline long run distances runners should really hit.
Here’s the minimum long run mileage to aim for so you can build enough endurance to maintain pace through the end of the race, while keeping injury risk low and the rest of your training on track.
For Beginner-Level Runners
If you’re training for your first marathon, your absolute minimum long run should be about 15 miles, Roberto Mandje, a former Olympic middle-distance runner and New York City-based run coach, previously told Runner’s World, but ideally you want to go up to 18.
Before building to that distance, though, beginners need to establish consistency. Mandje says he often starts newer runners with time-based run/walk sessions to get them used to running regularly, then gradually progresses them toward 10-plus-mile long runs. From there, they could begin taking on longer long runs.
Mandje says beginners should work up to at least two 18-mile long runs closer to peak training, before the taper, with a build lasting at least 16 weeks, but could stretch up to 20 weeks or more. This gives runners enough room to increase both weekly mileage and long-run distance safely.
Remember: The goal isn’t to nail one massive long run, but to teach the body to run longer, handle more time on feet, and recover well enough to keep training week after week. And in some cases, abandoning a mileage target completely may be the ideal strategy.
Kim Conley, a former U.S. 5,000-meter Olympian and Flagstaff-based running coach, previously told Runner’s World she capped beginner long runs at three hours, regardless of mileage. Runners averaging 11-plus minutes per mile may find Conley’s suggestion especially useful because pushing toward 18, 19, or 20-mile long runs could turn a quality run into a four-plus-hour slog and raise injury risk, she explains.
For Intermediate-Level Runners
Runners who already train consistently, have a few marathons under their belts, and may be chasing a time goal should expect the minimum long run to start a bit higher.
Intermediate runners should complete a handful of 16- to 20-mile long runs during marathon training, with 16 miles serving as a bare minimum requirement and 20 miles becoming the ideal target to work up to.
Mandje guides his runners to slightly increase their weekly long runs throughout their training plan as fitness improves and their bodies are able to handle more mileage.
For intermediate runners with more ambitious time goals—think breaking 3:30—Conley recommends completing at least two 18- to 20-mile long runs, including one effort with race-pace miles in the middle.
A workout like this teaches runners how their goal pace should feel when they’re already carrying fatigue. It also becomes a gauge to determine if the selected pace is sustainable.
Runners in the 3:30 to four-hour range may still progress to one or two 20-mile long runs around their peak (potentially including race-pace miles), but likely won’t have the same weekly mileage as faster runners.
The key: Once you’ve raced a few marathons and know what you’re getting into when you begin training, your long run should grow along with your weekly mileage.
For Advanced-Level Runners
Aiming to run under 2:30? At this level, the long run is less about hitting one bare-minimum distance and more about making sure your weekly mileage is high enough—and purposeful enough—to support it, both coaches suggested.
For fast time goals like this, peak mileage will likely need to reach at least 70 to 80 miles per week, depending on injury history, training background, and how well the athlete responds to volume, Mandje explains.
With a strong aerobic foundation, advanced runners should be able to ramp up into long runs in the high teens fairly quickly, then progress toward 20- to 22-mile efforts during peak training. Conley says her 2:30-level marathoners typically complete at least two 20-mile long runs, plus one run of up to 22 miles.
If you’re not a high-mileage runner—no matter your experience level or race goal—it’s more important to make each mile you do run serve the larger purpose of race-day performance. That means balancing long runs and easy mileage with quality workouts, such as interval sessions, threshold efforts, and race-pace miles, so your longest runs prepare you not just to cover the marathon distance, but to run it strong and fast.
Matt Rudisill is an Associate Service Editor who has been with Runner's World since 2025. A Nittany Lion through-and-through, Matt graduated from Penn State in 2022 with a degree in journalism and worked in communications for the university's athletic department for three years as the main contact and photographer for its nationally-ranked cross country and track & field teams. Matt was also heavily involved in communications efforts for Penn State football, men's basketball, and women's gymnastics. In his role with Runner's World, Matt has interviewed Olympians, world champions, and countless experts in the field to create service content that helps runners of all ages and experience levels train smarter and race faster. When he’s not out jogging, Matt can be found tweeting bad takes about the Phillies or watching movies.