12-Week Marathon Training
Who a 12-week build suits, what it assumes and how the weeks progress.
- Written by
- YourMarathonPace
- Published
- 9 November 2026
This guide is general information, not medical or coaching advice. It has not yet been reviewed by a qualified coach. Speak to a doctor before starting a new training programme, especially if you have a health condition or injury.
Who 12 weeks suits
A 12-week plan is a short build. It works best for runners who are already training regularly, for example after a recent half marathon, or for people who have run a marathon before and kept their fitness. It is not a good choice if you're starting from little or no running.
Starting fitness required
As a rough guide, you should be comfortably running three to four times a week and able to manage a long run of around 10–13 miles (16–21 km) before week one. If you're not there yet, choose a 16- or 20-week plan instead.
Week-by-week structure
Most 12-week plans run in blocks. There are about four weeks of building volume, four weeks of the hardest training with the longest runs and goal-pace work, then a taper. Many plans include an easier week every third or fourth week. Most of your running should be at an easy, conversational effort, with one or two harder sessions a week at most.
Long runs and taper
Long runs usually build to one or two runs of around 18–20 miles (29–32 km), with the longest about three weeks before race day.
Most plans cut weekly mileage over the final two to three weeks while keeping a little running at goal pace, so your legs stay sharp. Expect to feel restless or sluggish during the taper. That's normal, and it isn't a sign you've lost fitness. Don't try to make up missed sessions in race week.
Risks of a short build
Increasing your training quickly is linked to a higher risk of injury. With only 12 weeks, it's tempting to jump mileage or squeeze in extra sessions. Build steadily, take your easy days easy, and treat pain that changes how you run as a reason to stop and get it checked.
Sources
- The training–injury prevention paradox: should athletes be training smarter and harder? — British Journal of Sports Medicine (Gabbett, 2016)
- What is best practice for training intensity and duration distribution in endurance athletes? — International Journal of Sports Physiology and Performance (Seiler, 2010)
This guide is general information, not medical or coaching advice. It has not yet been reviewed by a qualified coach. Speak to a doctor before starting a new training programme, especially if you have a health condition or injury.