The Minimum Long Run You Need to Finish a Half Marathon

You don’t have to run 13.1 miles in training to be ready for a half marathon, but you do need a long run that’s long enough.

Here’s how to find the minimum that will still get you to the finish line, what works for most runners and most training plans, and when it actually makes sense to go longer.

How long your longest run should be for a half marathon

A widely used target for finishing strong is building your long run to 10–11 miles (16–18 km) at an easy, conversational effort. Getting comfortable at that distance gives you the endurance required to cover 13.1 miles on race day.

3 reasons why the 10–11-mile long run is enough:

It gets you close enough to race distance to practice pacing under fatigue.
It gives you real time-on-feet without the deep recovery hangover that can wreck the next week of training.
It’s long enough to rehearse fueling. For runs lasting over an hour (75+ minutes), sports nutrition guidelines commonly recommend 30–60 grams of carbohydrate per hour, so, this is where you test the exact nutrition and timing you’ll use on race day.

How long your long run should be, also depends on your background and what you want from the race:

For first-time half marathoners
For a debut at 13.1, reaching 10 miles (16 km) is enough for most runners to cover the race distance. Extending to 11 miles (18 km) is an optional confidence boost and makes sense only if you have sufficient recovery.

For slow runners expecting 2:30+ finish times
When projected finish time extends beyond two and a half hours and your long run includes extended walking segments, distance becomes less useful than duration.

In this case, the longest long run should usually cap at about 2:00–2:15 on your feet, even if that equals only 8–10 miles (13–16 km). Extending much beyond that often increases recovery time without adding meaningful endurance benefit.

For more advanced runners chasing time goals
In plans aimed at a time goal, the long run often reaches 12–14 miles (19–23 km). The final miles are frequently run at goal half-marathon effort to practice locking into race rhythm on tired legs.

Why most runners don’t need to run 13.1 in half marathon training

Running 13.1 in training can be useful for certain experienced runners, but it also has a cost. It’s a bigger fatigue bill to pay, and the payment often comes due in the middle of the week, right when your tempo run or intervals are scheduled.

As a result, instead of arriving fresh for your midweek speed workout, you’re still carrying the long-run fatigue.

A lot of race plans that include long runs longer than half-marathon distance are built for performance goals (like sub-2:00, sub-1:45), not for simply finishing.

If you’re not chasing a time goal and your priority is to finish strong, build your longest run to 10–11 miles and let the race-day atmosphere carry you through the final stretch.

How short can your longest run be and still finish a half marathon

For most runners, the lowest effective long run sits in the 9–10-mile (14.5–16 km) range. That distance lets you get through the final miles without having to switch to a walk.

If you’ve recently raced a 10K and can cover that distance comfortably from start to finish, the minimum moves slightly lower. In that case, a long run of 8–9 miles (13–14.5 km) is usually sufficient, because the aerobic load and pacing under fatigue are already familiar to you.

If you’re planning walk breaks or expect to finish slower than 2:30, use duration instead of distance. Then the minimum longest run should be about 1:45–2:00 on your feet.

Minimum long run:

First-time half marathoners: 9–10 miles (14.5–16 km)
Runners who can already cover a 10K comfortably: 8–9 miles (13–14.5 km)
Run–walk or 2:30+ finish time: about 1:45–2:00 on your feet

Anything shorter usually leads to walk breaks in the final miles instead of a continuous run.

When to schedule your longest run before a half marathon

The peak long run helps most when it happens soon enough to absorb the fitness, but not so close to race day that you carry fatigue to the start line. Having that in mind, schedule your peak long run three weeks before race day.

A common half-marathon taper lasts about two weeks. Your final long run should be shorter than the previous one and done at an easy effort.

A practical example (race on Sunday):

3 weeks out: peak long run 10–11 miles (16–18 km) easy
2 weeks out: long run 8–9 miles (13–14.5 km) easy, practice fueling
Race week: one short speed workout early in the week, then keep runs short and relaxed; the day before can be 25–30 minutes easy

The bottom line

The long run remains the key session of the week because it’s where you build the endurance, pacing control, and fueling routine that determine how you finish.

Most runners don’t need to cover the full 13.1 miles in training to be ready for race day. A longest run of 10–11 miles (16–18 km) prepares you to run the distance comfortably and finish strong. Go longer only when you have a time goal and can handle higher weekly mileage.

The true minimum sits lower and depends on your background. If this is your first half, 9–10 miles is usually enough. If you already handle a 10K comfortably, 8–9 miles can work. If your plan includes extended walk breaks, the key number is about two hours on your feet, not the distance on the watch.