Running
Half Marathon Training Guide: Building to 13.1 Miles
A twelve-week half marathon plan for runners with a 10K base — long-run progression, fueling practice, race-day pacing, and how to choose a course that suits your strengths.
Why the half marathon is the sweet spot
The half marathon (13.1 miles) has become the most popular endurance distance in the United States, and for good reason. It demands genuine endurance — you cannot bluff your way through thirteen miles — but the recovery is manageable, typically a week to ten days, compared to the three to four weeks a marathon requires. You can race two or three half marathons a year and still train consistently, which makes it the ideal distance for runners who want to race often without sacrificing their training base.
The half marathon also sits at the intersection of speed and endurance. A well-trained runner races a half at roughly their lactate threshold pace, which means the tempo work from 10K training transfers directly. The added challenge is the long run: you must build the capacity to stay on your feet for two to three hours, and that requires a progressive long-run build that the shorter distances do not. Browse running races to find half marathons that fit your schedule.
The twelve-week progression
A runner with a 10K base needs twelve weeks to build to a half marathon. The plan has four runs per week: an easy run, a speed or tempo session, a mid-length steady run, and a long run that grows from five miles to twelve miles. The long run is the centerpiece — it should peak at ten to twelve miles about two weeks before the race, then taper down in the final fortnight. You do not need to run the full 13.1 in training; if you can run twelve miles comfortably, the adrenaline and crowd of race day will carry you the rest.
The weekly long run should grow by no more than one to two miles per week, with a cutback week every third or fourth week where the long run drops by 30 to 40 percent. This progressive overload with built-in recovery is what lets your body adapt without breaking down. If you reach a long-run distance and feel excessively sore or fatigued for more than two days, hold that distance for an extra week before pushing further. Use the race calendar to find a half marathon twelve to fourteen weeks out.
Fueling for the long effort
The half marathon is the shortest distance where in-race fueling genuinely matters. Your body stores enough glycogen for roughly 90 minutes of running; if your half marathon will take longer than that, you will deplete your reserves and hit the wall in the final miles. The solution is to take 30 to 60 grams of carbohydrate per hour during the race, starting at mile three or four — not when you feel tired, because by then it is too late.
Practice your fueling in every long run. Gels, chews, or sports drink all work; the key is to use the same product and flavor you will use on race day, at the same intervals. Take a gel with water, not sports drink, to avoid stomach upset from concentrated sugar. If you have never fueled during a run, start with one gel at the halfway point of a long run and build from there. A half marathon is also the first distance where pre-race dinner and breakfast matter — eat a familiar, carb-focused meal the night before and a light breakfast two hours before the gun.
Pacing and race-day execution
The half marathon should be paced as a long tempo with a gradual build. Run the first three miles at your long-run pace — deliberately slower than your goal race pace. Settle into your goal pace from mile three to mile ten, and treat the final 5K as a race within the race: if you feel strong, push; if you feel tired, hold. The most common error is running the first 5K at goal pace or faster, which depletes glycogen and turns the final three miles into a death march.
Line up in the corral according to your expected finish time, not your goal time — starting too far forward means weaving through slower runners, and starting too far back means the first mile is too slow. If the race has pace groups (runners holding signs for target finish times), join one for the first half of the race and let them do the pacing work. Save your race to My Season so the countdown keeps your long runs honest as race day approaches.
Choosing a course that suits you
Half marathon courses vary enormously, and the right choice depends on your strengths. Flat, fast courses (like a rails-to-trails or a coastal road) are ideal for a personal best. Urban city marathons often have a half option with crowd support and closed roads. Trail half marathons offer scenery and softer surfaces but demand trail shoes and attention to footing. Use the race directory to filter by state, date, and distance, and check the elevation gain on each race page.
For your first half marathon, strongly prefer a flat, well-supported course with a generous time limit. The goal is to finish feeling strong, not to suffer through a hilly, under-supported race that sours you on the distance. After your first, you can seek out more challenging courses or chase a personal best. The natural progression after a half is the full marathon training guide, but many runners happily race half marathons for years without ever moving up.