12-Week Half Marathon Training Plan

If you want to understand in depth how to prepare for a half marathon (times, kilometers, mistakes, and strategy), you can consult our complete guide on how to prepare for a half marathon.

In this article, you will find a 12-week half marathon training plan, designed to help you prepare for the distance in a progressive and structured way. This is a guideline intended for runners who are already able to complete about 10 kilometers comfortably and with some proficiency, and who wish to make the leap to 21 kilometers with confidence.

This half marathon training plan combines runs, quality sessions, long runs, and recovery periods with the aim of developing the necessary endurance to tackle a half marathon safely and confidently. The progression of volume and intensity is designed to allow for a gradual adaptation of the body to the effort required by this distance.

Like any general plan, this half marathon training plan should be adapted to the characteristics, experience, and availability of each runner. Use it as a reference structure to organize your next 12 weeks of preparation and arrive on race day in the best possible condition.

 

Before starting the plan: important recommendations

Before starting this 12-week half marathon training plan, it is important to consider some basic aspects that can make a difference in your preparation.

Start with a minimum training base

This plan is designed for runners who can already run around 10 kilometers continuously and comfortably. If you don’t have that base yet, it is best to consolidate that distance first before starting specific preparation for the 21 kilometers.

Listen to your body

The training progression is designed to gradually increase the workload, but each person responds differently to training. If you notice excessive fatigue, discomfort, or lack of recovery, it is advisable to adjust the volume or intensity of the sessions.

Prioritize regularity over intensity

Consistency is one of the most important factors for preparing for a half marathon. It is preferable to train regularly for several weeks than to do very demanding sessions occasionally.

Respect rest and recovery days

Rest is also part of training. It allows the body to adapt to workloads and reduces the risk of injury.

Adapt the plan to your availability

This program is a guideline training structure, so you can adjust it to your personal calendar, experience, or sensations during preparation.

12-Week Half Marathon Training Plan

And now, below is a guideline structure for a 12-week half marathon training plan. The progression combines easy runs, quality sessions, and long runs with the aim of improving endurance and arriving on race day with confidence.

Weeks 1-4: Base Building

During these first weeks, the aerobic base is built that will support the rest of the training.

• 2 easy runs (6-8 km)
• 1 progressive long run (10-12 km)
• 1 optional strength session

In this phase:

• Comfortable, conversational pace (work in Z2 or VT1).
• Do not prioritize speed.
• Introduce compensatory (strength) work for core and lower body.

Weeks 5-8: Introduction of Quality

In this block, quality work is introduced to improve efficiency and start approaching race pace. (Z3-Z4 or VT2).

• 1 easy run
• 1 tempo session (e.g., 5×1000 m, Fartlek by time)
• 1 medium run (10-12 km)
• 1 long run (14-16 km)

Here begins the specific work:

• Paces close to race goal.
• Learn to manage accumulated fatigue.

Weeks 9-11: Specificity

Here, training becomes more specific, with sessions aimed at replicating the real demands of the race.

• Long intervals (3×3000 m or 2×5000 m)
• Controlled runs at target pace
• Maximum long run (18-19 km)

Contrary to what many runners believe, it is not necessary to complete the full 21 km in training. Physiological adaptation will already be built if the plan has been progressive.

Week 12: Tapering or “Peak Performance”

This last week is focused on reducing the load and arriving on race day feeling good and without accumulated fatigue.

• Reduce volume by 40-50%
• Maintain some intensity
• Prioritize rest and sleep

 

Phase	Weeks	Main Goal	Recommended Workouts	Key Aspects
Base Building	1-4	Improve basic aerobic endurance.	2 easy runs of 6-8 km. 1 progressive long run of 10-12 km. 1 optional strength session.	Maintain a comfortable, conversational pace, working in Z2 or VT1. Do not prioritize speed. Introduce compensatory strength work, especially core and lower body.
Introduction of Quality	5-8	Improve aerobic efficiency and race pace, working in Z3-Z4 or VT2.	1 easy run. 1 tempo session, such as 5×1000 m or fartlek by time. 1 medium run of 10-12 km. 1 long run of 14-16 km.	Start working on paces close to race goal. Learn to manage accumulated fatigue. Begin specific half marathon training.
Specificity	9-11	Simulate real race conditions and consolidate race pace.	Long intervals, such as 3×3000 m or 2×5000 m. Controlled runs at target pace. Maximum long run of 18-19 km.	It is not necessary to complete the full 21 km in training. Physiological adaptation will be built if the plan has been progressive. Work on confidence and effort management.
Tapering or Peak Performance	12	Arrive fresh on half marathon race day.	Reduce training volume by 40-50%. Maintain some intensity. Prioritize rest and sleep.	Avoid accumulating fatigue in the last few days. Maintain good sensations without overdoing it. Arrive rested, active, and confident for the race.

 

The most common mistake when reaching week 12, especially for beginners, is to overtrain due to insecurity; in the last week of race preparation, you should prioritize rest and recovery to arrive fresh on race day.

Conclusion

Preparing for a half marathon is a progressive process that requires time, consistency, and proper planning. A 12-week half marathon training plan allows you to develop the necessary endurance to tackle the 21 kilometers with greater safety and confidence.

If you can already complete 10 kilometers with proficiency, following a training structure like the one presented in this article can help you organize your preparation and gradually make the leap to the half marathon.

Remember that each runner has a different adaptation pace. Listening to your body, respecting recovery, and maintaining regularity in training are key to arriving on race day in the best possible condition and enjoying the experience of completing the 21 kilometers.

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