How Long Should Your Long Run Be for a Half Marathon?
The long run is one of the most important sessions in your half marathon training.
It is also one of the sessions runners are most likely to overcomplicate.
How far should you run? Do you need to reach 21.1 kilometres before race day? Should your long run get longer every week? Should you include race pace? And if your half marathon is likely to take you two-and-a-half hours, does that mean you need to run for two-and-a-half hours in training?
My approach is based primarily on duration rather than distance.
For most half marathon runners, I will build the long run progressively towards a maximum of around two hours. Some runners will reach that. Others won’t. Faster runners may comfortably cover more than 21.1 kilometres within that time, while a more recreational runner might only reach 16 kilometres or less during their longest training run.
That’s okay.
The purpose of the long run isn’t to prove that you can cover 21.1 kilometres before race day.
It’s to create the aerobic adaptations and endurance you need to perform well over the half marathon distance — without creating so much fatigue that the long run compromises the rest of your training.
Why the Long Run Matters for Half Marathon Training
Although runners often think of quality training as intervals, hill repetitions, threshold sessions and tempo runs, I consider the long run one of the most important — if not the most important — quality sessions for half marathon performance.
That doesn’t mean it needs to be run hard.
In fact, for the vast majority of athletes I coach, most of the long run is completed at Level II — Endurance/Conversational intensity.
The objective is to spend quality time developing the aerobic system.
As you run aerobically, air moves into the lungs, oxygen moves out of the air across into the bloodstream and is transported by the cardiovascular system to the working muscles. Within those muscles, oxygen contributes to aerobic energy production in the mitochondria.
Consistent aerobic training creates adaptations throughout that system, including increased mitochondrial density and capacity within the muscles.
In simple terms, we’re developing your ability to produce energy aerobically and sustain running efficiently for longer.
And that takes time.
That’s one reason the long run is so valuable.
It gives us an extended period at Level II to stimulate those adaptations without the substantially greater training cost that would come from trying to race the session.
Your Long Run Should Usually Be at Level II
One of the most common mistakes I see is runners doing their long runs too fast.
You’re not racing your half marathon every weekend.
If every long run becomes a test of how fast you can cover the distance, you’re changing the purpose of the session.
Instead of accumulating controlled aerobic work, you’re creating considerably more fatigue. That can increase the recovery required afterwards and potentially compromise the training you have planned for the following days.
For most athletes, the prescription is straightforward:
Run your long run at Level II.
You should be running at an endurance/conversational intensity that allows you to accumulate time on your feet without turning the session into a race.
There are two main exceptions within my programmes:
- Stride-outs towards the end of the long run.
- Progressive long runs for selected advanced athletes.
I’ll come back to both of those shortly.
How Long Should Your Long Run Be?
For most half marathon runners, I generally cap the long run at around two hours.
That doesn’t mean everybody has to reach two hours.
Nor does it mean two hours is an absolute ceiling that can never be exceeded.
It’s a practical guideline based on balancing the benefit of the session against the training stress and recovery cost it creates.
As the long run gets longer, there comes a point where the additional training benefit may not justify the additional recovery required.
If I give an athlete an excessively long run on the weekend and they’re still carrying substantial fatigue when they reach their next important training session, that long run hasn’t occurred in isolation.
It has affected the rest of the programme.
That’s an important concept.
A training session shouldn’t be judged solely by what it achieves on the day. We also need to consider what it allows you to do afterwards.
For the majority of half marathon runners, approximately two hours gives us plenty of opportunity to develop endurance without unnecessarily increasing the recovery burden.
Do You Need to Run for Two Hours Before a Half Marathon?
Preferably, I’d like a beginner runner to gradually build towards a two-hour long run before their half marathon, if we have enough time to do so safely.
But sometimes we don’t.
An athlete might begin preparing relatively close to their event. Their training history may mean we can only build their longest run to 90 minutes.
In some cases, it might be only 80 minutes.
Does that mean they shouldn’t start the half marathon?
Absolutely not.
We work with the preparation time we’ve got.
If their longest training run is 90 minutes and the half marathon takes them considerably longer, then yes, race day is going to be a substantial step up.
It will create more fatigue. They’ll probably need more recovery afterwards.
But that’s not necessarily a problem.
The goal event is supposed to be a challenge.
For one athlete, the challenge might be covering 21.1 kilometres for the first time.
For another, it might be trying to run the distance substantially faster than they’ve ever run it before.
There’s no rule saying you must have completed a 1:45, two-hour or any other arbitrary long-run duration before you’re allowed to attempt a half marathon.
We simply want to build as much appropriate preparation as the available time and athlete’s circumstances allow.
Do You Need to Run 21.1 km Before Race Day?
This is one of the most common questions I hear.
No. You absolutely do not need to run 21.1 kilometres in training before completing a half marathon.
Some faster runners will cover the half marathon distance during an ordinary long run.
If an athlete can comfortably cover more than 21.1 kilometres during a two-hour Level II run, there’s nothing particularly remarkable about them passing the half marathon distance during training.
But consider a recreational runner whose Level II pace means a two-hour run allows them to cover 16 kilometres.
I’m not going to add another five kilometres simply because they need psychological proof that they can cover 21.1 kilometres.
Those extra kilometres might substantially increase the duration and recovery cost of the session.
And what have we actually achieved?
We’ve potentially compromised several subsequent training sessions simply to tick off an arbitrary distance.
The distance you cover is an outcome of your long-run duration and pace. It isn’t the measure of whether the session was successful.
A 90-minute Level II long run can be an entirely appropriate session for two runners who cover very different distances.
Where Should Your First Long Run Start?
Your first long run shouldn’t be based on where you eventually want to get to.
It should be based on where you are now.
As a rough rule of thumb, I’ll look at the athlete’s longest run during approximately the previous six weeks, assuming they’ve remained healthy and aren’t returning from injury.
Let’s say you are a beginner who can run continuously for 30 minutes.
If you ran 30 minutes last week and you’ve been training consistently, I might make your long run the following week – 35 minutes.
But what if the last time you ran for 30 minutes was six weeks ago?
I’m probably going to start you at 30 minutes rather than immediately increasing it.
The same principle applies to a more experienced athlete.
If you’ve recently completed a 90-minute long run, there’s no reason for me to send you back to 60 minutes simply because you’ve started a new training programme.
If you ran 90 minutes the previous week and have been consistently completing similar training, your next long run might be 1:35hr or perhaps 1:40hr.
Your starting point should reflect your recent training history, not an arbitrary Week One number on a generic schedule.
How Quickly Should Your Long Run Increase?
I don’t like massive jumps in long-run duration from one week to the next.
As a general guideline, we’re looking at increases of around 5–10% in duration, although I don’t treat that as an inflexible mathematical rule.
For beginners, I often make this even simpler:
Add five minutes.
A progression might look like:
45 minutes → 50 minutes → 55 minutes → 60 minutes.
Once an athlete is comfortably running beyond an hour and has more training history behind them, increases of around 10 minutes can sometimes be appropriate.
For example:
70 minutes → 80 minutes → 90 minutes.
Mathematically, some of those increases exceed 10%.
That’s okay.
The athlete isn’t a spreadsheet.
Their training history, consistency, previous long runs, recovery and experience all influence how aggressively we can progress the session.
The principle is more important than rigidly applying a percentage:
Build the long run gradually from what the athlete is already capable of handling.
Your Long Run Doesn’t Have to Increase Every Week
Progression also doesn’t mean endlessly adding five or ten minutes every weekend until race day.
Training needs periods where we absorb the work we’ve already completed.
Recovery weeks can reduce training load before we begin progressing again.
The long run therefore needs to be viewed as one component of the complete training programme rather than as an independent challenge that must get harder every Sunday.
There will also eventually be a taper.
My final full long run will typically occur two weeks before the half marathon.
The long run on the weekend immediately before the race will be significantly reduced as part of that two-week taper.
At that stage, we’re no longer trying to build more endurance.
We’re trying to arrive at the start line ready to use the fitness we’ve already developed.
Why I Usually Cap the Long Run at Around Two Hours
The two-hour guideline comes back to cost versus benefit.
Could you run longer?
Of course.
Would running for two-and-a-half or three hours create more training stress than running for two hours?
Almost certainly.
The question is whether that additional stress gives us enough additional benefit to justify the recovery cost.
For most half marathon runners, it doesn’t.
If a three-hour training run leaves you so fatigued that your training for the next several days is compromised, we’ve potentially sacrificed multiple sessions for one oversized long run.
That’s not how I want to build a half marathon programme.
My goal isn’t to maximise the amount of training you can survive.
I want to minimise the amount of training required to achieve your goal.
There are exceptions.
With high-performing runners who have a substantial training history and the ability to tolerate the workload, I may occasionally prescribe a long run of around two-and-a-half hours, perhaps once a month.
But that’s very different from suggesting every recreational half marathon runner needs to keep extending their long run beyond two hours.
Most don’t.
Should You Include Stride-Outs in Your Long Run?
Once an athlete is comfortably running beyond approximately an hour, I typically start including four 20-second Level V stride-outs towards the end of the long run.
These aren’t intended to turn the session into a hard workout.
The vast majority of the session remains at Level II.
I spread the stride-outs five minutes apart and ensure the final stride-out is completed with 10 minutes of Level II running remaining.
For example, during a 90-minute long run:
- 65:00: 20-second Level V stride-out, then return to Level II
- 70:00: 20-second Level V stride-out, then return to Level II
- 75:00: 20-second Level V stride-out, then return to Level II
- 80:00: 20-second Level V stride-out, then return to Level II
- 80:20–90:00: continue at Level II to finish the run
In practical terms, after each 20-second stride-out you have approximately 4 minutes 40 seconds back at Level II before beginning the next one.
After the fourth, you have almost 10 minutes of controlled Level II running before finishing.
That gives us an effective cool-down rather than having the athlete complete their final stride-out and immediately stop.
Long Runs During the Foundation and Injury Prevention (FI) Phase
During the Foundation and Injury Prevention (FI) phase, I don’t see a need for progressive long runs.
We’re building the aerobic foundation.
The long run is therefore predominantly Level II.
Once the athlete is comfortably beyond an hour, I’ll generally incorporate the four 20-second Level V stride-outs described above.
But that’s enough.
We don’t need to keep adding intensity simply because we can.
Remember what we’re trying to achieve during this phase: consistency, aerobic development and the ability to tolerate gradually increasing training.
Long Runs During the Early Quality (EQ) Phase
The philosophy remains similar during the Early Quality (EQ) phase.
The athlete’s dedicated quality training elsewhere in the week may now include hill repetitions and, where appropriate, some tempo work.
That doesn’t mean the long run also needs to become substantially harder.
For most athletes, it remains:
Level II + 4 × 20-second Level V stride-outs towards the end.
This allows us to continue developing endurance while the athlete absorbs the additional quality work being introduced elsewhere in their week.
What About Progressive Long Runs?
Progressive long runs can be extremely useful.
But most half marathon runners don’t need them.
I reserve these sessions predominantly for faster, more advanced athletes who have a strong training history, have completed a good build-up and can recover from the additional training stress.
They’re most likely to appear during the Transition Quality and Final Quality phases.
Even then, they aren’t automatically prescribed to everybody.
Some athletes towards the upper end of capability may have progressive long runs introduced during Final Quality. The fastest and most experienced athletes may use them during both Transition Quality and Final Quality.
But the vast majority of recreational half marathon runners can prepare very successfully without them.
What Does a Progressive Long Run Look Like?
A progressive long run doesn’t mean going out for your normal long run and deciding to hammer the final few kilometres because you’re feeling good.
It’s a structured workout.
A substantial portion of the session remains at Level II before intensity is deliberately increased.
For example, one of the progressive long runs I use is:
60 minutes Level II → 40 minutes Level III → 10 minutes Level IV → 10 minutes Level II cool-down.
That’s a two-hour workout, but notice that the first hour is still Level II and the final 10 minutes return to Level II.
The progression has a purpose.
We’re asking an appropriately prepared athlete to increase their intensity after already accumulating fatigue, while maintaining control and then finishing with a proper cool-down.
That is very different from racing the last half of every Sunday long run.
And because it’s a demanding session, it has to earn its place in the programme.
For most athletes, a conventional Level II long run remains the better choice.
Don’t Turn Every Long Run Into a Race
This deserves repeating.
Your long run isn’t your weekly half marathon time trial.
Running it harder can make the workout feel more productive because you’re tired afterwards.
But fatigue isn’t the objective.
Adaptation is.
If you’re already completing a dedicated quality session during the week — perhaps hill repetitions, threshold intervals or tempo work depending on your training phase — you don’t need to prove your fitness again during the long run.
Allow Level II to do its job.
Accumulate aerobic work.
Build durability.
Develop your ability to remain efficient for longer.
Then recover sufficiently to complete the next session well.
Good training isn’t about making every workout difficult.
It’s about giving each workout a clear purpose.
Use Your Long Run to Practise Race-Day Nutrition
Your long run has another important role as your half marathon approaches.
It’s your nutrition laboratory.
Don’t wait until race morning to discover whether your planned breakfast works, whether you tolerate a particular gel or how you’re going to manage hydration.
Practise these things during your long runs.
That might include your race-morning breakfast before training, your planned gels during the run, fluids, electrolytes and caffeine if you intend to use it.
The longer sessions give you the opportunity to discover how your stomach responds after you’ve already been running for a substantial period.
My rule is simple:
Nothing new on race day.
I’ve covered this in considerably more detail in my complete guide to half marathon nutrition:
Half Marathon Nutrition: What to Eat and Drink Before, During and After Your Race
Your Longest Run Is Not Your Half Marathon Prediction
Don’t make the mistake of looking at your longest training run and using it as a test of whether you’re capable of completing your race.
If you’ve built to two hours at Level II but haven’t covered 21.1 kilometres, that’s not evidence that you can’t complete the distance.
Likewise, if you’re a faster runner and cover 22 or 23 kilometres during a comfortable long run, that doesn’t mean you should start racing your long runs to find out how fast you can cover the half marathon distance.
Training and racing have different purposes.
Training creates the adaptations.
Race day is where you use them.
How Long Should Your Half Marathon Long Run Be?
So, if you’re looking for one number, I’m deliberately not going to give you one.
Your appropriate long-run duration depends on:
- what you’ve been running recently;
- how consistently you’ve been training;
- your training history and experience;
- how many weeks you have before your event;
- how well you’re recovering;
- where you are within the training programme; and
- the demands of your goal.
A useful starting point is your longest healthy run from approximately the previous six weeks.
From there, gradually build the duration — often by around five minutes for newer runners and sometimes around 10 minutes for experienced runners who are already comfortable with longer durations.
For most athletes, work towards a ceiling of approximately two hours.
If you don’t have enough preparation time to reach two hours safely, don’t panic.
Build as far as your available training time reasonably allows.
And don’t chase 21.1 kilometres simply so you can say you’ve completed the distance before race day.
Ready to Take the Guesswork Out of Your Long Runs?
Knowing that your long run should build gradually is one thing. Knowing how long to run this week, when to increase it, when to back off, and how it fits alongside the rest of your training is another.
That’s where a structured half marathon programme can help.
Inside NZ Half Marathon Hub+, you’ll find structured programmes for different experience levels, preparation times and performance goals — with your long runs, quality sessions, steady running, recovery and taper already mapped out for you.
Rather than trying to decide each week whether your long run should be 70, 80, 90 or 120 minutes, you can follow a progressive programme designed to prepare you for 21.1 km without simply trying to maximise your training.
Build the long run you need — not simply the longest run you can survive.
The Bottom Line
Your half marathon long run should be long enough to develop your endurance, but not so long that its recovery cost compromises the rest of your training.
For most runners, that means gradually progressing towards approximately two hours, with the overwhelming majority of the session completed at Level II.
Once you’re comfortably running for more than an hour, I generally include four 20-second Level V stride-outs towards the end, with the final stride-out completed 10 minutes before finishing.
Only a relatively small group of suitably experienced athletes need progressive long runs during Transition Quality (TQ) and Final Quality (FQ) phases.
And you absolutely do not need to run 21.1 kilometres before your half marathon.
Some runners will cover it naturally during their training. Others won’t come close.
Both can arrive at the start line appropriately prepared.
Build gradually. Keep the purpose of the session clear. Practise your race-day nutrition. Allow yourself to recover.
Then save the real 21.1-kilometre challenge for the day that matters — race day.
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