For many runners, the half marathon plan starts something like this: “I can run 10 km, so now I'll double my training, and then I'm ready to cross the finish line at a half marathon.” Simple. Logical. And not quite right. A good half marathon training isn't just about doing twice as much as usual. It's a distance in itself that requires targeted training. Otherwise, you often end up among those runners who feel great after 8 km but are completely done when they hit 18.
For some, a half marathon is about completing their first 21.1 km. Here, time isn't the most important factor. For others, it's about running more controlled, managing pace and energy intake, so everything comes together, and you can stand at the finish line with a new PR. Regardless of your goal, the distance requires the same three things: a solid aerobic foundation, respect for pace, and a plan that suits your level. That's exactly what our half marathon calculator and 16-week programs are built for.
What does it take to run a half marathon?
A half marathon is an aerobic endurance distance, and the body must master three physiological parameters to handle it well.
- Your VO2max (maximum oxygen uptake) sets the limit for how much oxygen your circulatory system can transport and your muscles can utilize during work.
- Your lactate threshold sets the limit for how hard you can run over time. Above the threshold, fatigue accumulates faster than the body can remove it.
- Your running economy describes how efficiently you use energy per kilometer. Two runners with the same VO2max can perform differently because one utilizes energy better.
The three parameters are not improved by the same training. Simply put, easy long runs build your aerobic foundation, intervals increase your VO2max, and threshold runs train the body to work efficiently close to the limit. Therefore, a half marathon program isn't just “run more,” but a targeted combination of training forms that together prepare you for 21.1 km. That's precisely the approach our programs are based on.
Choose the right track in the calculator
Both our programs span 16 weeks, and it's not by chance. It takes time to significantly improve your form, whether you're new to the distance or chasing a PR. The programs are structured in phases that gradually increase the load. There are planned lighter weeks along the way, where the body gets a chance to recover and convert training into real progress. The last two weeks before the race, the volume is deliberately reduced in a taper period, so you stand at the start line with fresh legs and energy.
Both programs are built around pace, so you need a
or another device that can show you your pace along the way.
1. My first half marathon
This program is developed for you who can currently run about 10 km and dream of doubling the distance. You enter your current 10 km time, your weekly mileage, and your running frequency today. The calculator then estimates your half marathon time and gives you four training paces: Easy, Steady, Tempo, and Interval.
The program starts with three weekly sessions and later adds a fourth, depending on your starting point. Your long runs are built up slowly and safely from 10 km to 20 km, peaking in week 11. Finally, the training is tapered down in a planned taper, so you are sharp at the start line.
The program is targeted at runners with a 10 km time between 30 and 75 minutes. If you run 10 km in more than 75 minutes, we recommend starting with our 10 km program to build a stronger foundation.
2. Get faster at half marathon
This program is for you who have already completed the distance but are chasing a new personal record. It is targeted at runners with a current time between 1 hour and 20 minutes and 2 hours and 45 minutes. You enter your current half marathon time and choose your current training frequency of 3, 4, or 5 days. The calculator tells you how much time improvement you can realistically expect and calculates five training paces: Easy, Steady, Tempo, Threshold, and Interval. The threshold pace corresponds to your race pace.
The long runs are built up from 14 to 22 km, peaking in week 11. Uniquely, the long runs from week 9 will include segments at your half marathon race pace. This trains you to maintain speed when your legs are already tired, just as it will feel on race day.
Understand your training plan and zones
When you read your program, you will encounter different training types:
- Interval training: Short, hard efforts with active breaks in the form of walking or light running in between. Intervals improve your maximum oxygen uptake and your running economy.
- Tempo run: Continuous running at a comfortably hard pace. You should be able to say short sentences but not hold a longer conversation.
- Threshold run: Training at the highest pace you can maintain over time without fatigue accumulating. It is close to your half marathon pace and is only used in the Get Faster program.
- Long run: Run at an easy pace. You should be able to speak in full sentences. If it feels slow, it's perfect, as the goal is to build your aerobic endurance. From week 9, some of your long runs will include segments at half marathon pace. These segments are placed at the end of the long run, so you practice maintaining pace with tired legs.
Energy on long runs
When your training runs start to exceed 15 km or about 75 minutes, the body's own carbohydrate stores often can't cover the entire run. This is one of the big differences between training for 10 km and a half marathon: you need to learn to refuel during the run.
, or are the most practical solutions. The most important thing is not what you choose, but that you practice taking in energy on your long runs. Your stomach needs to get used to digesting while running, and it's a skill that requires training like everything else. Start with small amounts early in the process and experiment, so you know exactly what works for you long before race day.
A good rule of thumb is to consume 30 to 60 grams of carbohydrates per hour on runs over 75 minutes. In practice, this corresponds to one gel approximately every 30 to 45 minutes. Also remember fluids and adjust the amount according to the weather and heat. Read more in our guide to energy and running.
FAQ: 5 quick questions about your half marathon training
What do I do if I miss a training session in my half marathon program?
Skip the session and continue with the program. Avoid “catching up” by running extra the next day. If you've been sick for several days, go back a week and build up slowly again.
Can I rearrange the training days in the program?
Yes. The program is a framework. The most important thing is to keep your rest days and avoid two hard sessions in a row. Recovery is especially important after hard sessions and long runs.
How long should my long runs be leading up to a half marathon?
In My First Half Marathon, the long runs are gradually built up to 20 km, so you get close to the distance without running the full 21.1 km in training. In Get Faster at Half Marathon, the long runs are built up to 22 km, as the program also trains you to maintain speed with tired legs.
Should I bring energy on my long runs?
Yes, as a rule of thumb when the runs last over 75–90 minutes. Half marathon demands more energy management than 10 km, so you should train in taking gels and fluids along the way.
When can I expect to notice progress in my training?
Most notice improvement after 4–6 weeks, depending on their starting point and consistency. The long runs feel easier, and the pace becomes more stable. The biggest progress often comes after 8–10 weeks, but it's the last weeks with consistency and tapering that prepare you to perform optimally on race day.
Looking for running programs for other distances?
Find ourprograms here:
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Have a great run out there!
