How to Train for Your First Half Marathon: A Step-by-Step Guide
Your first half marathon is the natural next step after the 10K, and it is also where many runners realize that just going out for a run is no longer enough. It is 21.1 kilometers: twice a 10K and, for most people, between an hour and a half and two and a half hours of effort. Good preparation is about building endurance little by little and reaching the start line rested. In this guide I explain where you should start from, how many weeks you need, how to organize your week, what to do with the long run and how to run on race day.
Before training for your first half marathon
Ideally you start the plan able to run about 10 kilometers, or 50 to 60 minutes non-stop, at a comfortable pace. If you aren’t there yet, build that base first.
With that base, a 10 to 12 week plan is enough for most people. If you run little or are coming back from an injury, give yourself 14 to 16 weeks and build up more calmly. Having some margin lets you skip a week for work or a cold without the plan falling apart.
How many days a week to train
Three days a week is enough to finish a half marathon, and four makes the preparation more comfortable. You don’t need more for a first one.
A typical four-day week would have an easy run midweek, a quality day (tempo or intervals), another easy run and the long run at the weekend. If you only have three days, drop one of the easy runs. And leave at least one rest day between the quality session and the long run, because those are the two most tiring days.
The long run, the session that matters most
This is the one that prepares you for the distance. Start with a long run of about 8 to 10 km and add 1 to 2 km each week, with an easier week every three or four so your body can absorb the work. The goal is to reach 16 to 18 km two or three weeks before the race.
You don’t need to run the full 21 km before race day. With well-run long runs of 16 to 18 km, the race-day adrenaline and the rest beforehand cover the rest. Going further in a first plan usually brings more fatigue than benefit.
The long run should be easy, at a pace where you can talk. If you struggle to hold back, have a look at the guide on how to train in zone 2. And use these runs to test what you plan to eat and drink in the race.
Training paces for a half marathon
Most of your kilometers, around 80%, should be easy. The rest is quality work, and for a half marathon two types of session work very well.
The first is tempo or threshold running: 15 to 30 minutes at a “comfortably hard” pace, which is quite close to the pace you will hold in the half. The second is short intervals, for example 6 to 8 reps of 800 meters, which add some speed and make race pace feel easier. You will find examples in the 10K interval workouts, which work perfectly here.
To know how fast each session should be, enter your latest 10K time in the training pace calculator. And if you want to understand each zone, I explain them in the guide on training paces.
How to build volume without getting injured
The typical mistake when preparing a first half marathon is trying to make up in two weeks what wasn’t done in two months. As a reference, don’t increase your weekly volume by more than about 10% at once, and respect your easier weeks.
Add a couple of short strength sessions a week too. Squats, lunges, glute bridges and calf raises are enough. If you notice a niggle that doesn’t go away after a couple of rest days, stop and get it checked; the guide on runner injury prevention lists the warning signs.
The last two weeks: arrive rested
In the two weeks before the race you cut your volume, which is known as tapering. Reduce your kilometers by 30 to 50% compared with your biggest weeks, but keep a bit of pace with a short session so your legs don’t go flat.
You won’t gain fitness in those weeks, you will only shed fatigue. It is normal to feel restless and want to run more. Resist: arriving fresh is worth more than one last long run. All the details are in the guide on tapering.
How to run your first half marathon
What pace to run
To estimate your time, enter your 10K result in the race time predictor. As a rough rule, a half marathon usually comes out at a little over twice your 10K time plus a few minutes. In a first half, set a realistic target pace and go even slightly slower than that in the first kilometers.
The most common mistake is starting too fast, carried away by excitement and the crowd. The seconds you gain at kilometer 3 cost you minutes after kilometer 15. Ideally you run even splits or finish a little faster.
Eating and drinking during the race
If you will take less than an hour and a quarter, drinking water to thirst is usually enough. If you will be out there longer, a gel or some sports drink around halfway helps you hold your pace at the end. Work out how many carbs you need with the race carb calculator, and always test what you plan to take in training.
What to eat in the days before and at breakfast is in the guide on what to eat before a race, and what you need to know about fluids and salts is in the one on hydration and electrolytes.
The day before and race morning
Pick up your bib early, lay out your kit the night before and don’t wear or eat anything new: no new shoes, shirt or gels. Get to the start with time to spare for the toilet and a warm-up of 5 to 10 minutes of easy jogging. If you are looking for your first half marathon, the race directory has events to choose from.
Conclusion
Preparing for your first half marathon is more about consistency than suffering. Start with a base of about 10 km, give yourself 10 to 12 weeks, train three or four days with most kilometers easy, build your long run up to 16 to 18 km, cut volume in the last two weeks and start race day slower than your body is asking for. Crossing that finish line for the first time is one of the best feelings running gives you. Choose well, run better.
Frequently asked questions
How many weeks do I need to train for my first half marathon?
If you already run about 10 km, 10 to 12 weeks is enough. If you are starting from less or coming back from an injury, 14 to 16 weeks lets you build volume calmly.
Do I need to run 21 km before the race?
No. Long runs of 16 to 18 km in the weeks before are enough for a first half marathon. The rest in the final weeks and the race atmosphere do the rest.
How many days a week should I train for a half marathon?
You can finish one on three days a week, and four makes it more comfortable. What matters is that one is the long run and another is a quality session, with the rest at an easy pace.
What pace should I run my first half marathon at?
Estimate it from your 10K time with a race time predictor and start a little slower than that pace in the first kilometers. It is better to build up than to fade at the end.
Do I need gels in a half marathon?
If you will take more than an hour and a quarter, a gel or sports drink around halfway usually helps. Test it in training first so you know it agrees with you.
