The half marathon: 10 to 16 weeks, built around your life
Most runners train for a half marathon in 10 to 16 weeks, running 3 to 5 days a week. If you already run a comfortable 10K, 10 to 12 weeks is plenty. Building the 13.1-mile (21.1K) distance from a lower base takes 14 to 16 weeks. The long run is the anchor of the whole block, and it climbs gradually toward 10 to 13 miles before you taper.
The half marathon is the sweet spot of distance running. It's a serious endurance challenge that genuinely respects a couple of months of training, yet it doesn't demand the 18- and 20-mile long runs, the total-life-takeover mileage, or the deep recovery cost of a full marathon. You can train for a strong half on three to five runs a week and still have a life. That balance is why it's the most popular serious race distance in the world.
How long you need
- Comfortable 10K already: 10 to 12 weeks to build to the distance and add race-specific speed.
- Running regularly but new to longer distances: 12 to 14 weeks.
- Newer runner building from a modest base: 14 to 16 weeks, so the long run can grow without spiking your injury risk.
The long run is everything
If you get one thing right in half training, make it the long-run progression. This is the run that teaches your body to keep moving efficiently for 90 minutes to two-plus hours. Build it gradually, adding roughly a mile or so each week with a lighter "cutback" week every third or fourth week, until your longest run reaches somewhere between 10 and 13 miles. Run most of it easy and conversational; the goal is time on your feet, not speed. Rushing the long-run build is the single most common way people get hurt before race day.
The quality sessions that matter for the half
The half is run near your threshold, so threshold work is your bread and butter, complemented by segments at race pace:
- Tempo Run — sustained comfortably-hard effort that raises the pace you can hold for the distance.
- Cruise Intervals — threshold effort in repeats with short recoveries, letting you bank more quality time at pace.
- Half-pace work in the long run — rehearse race effort by finishing part of a long run at goal half-marathon pace.
- Progression Long Run — start easy and gradually lift the pace so the final miles are quicker, training you to stay strong when tired.
Fueling: don't skip it
Above about 75 to 90 minutes of running, your body starts running low on stored carbohydrate. For most people that means taking in some carbohydrate during the half, often a gel or two, plus water. Practice your fueling on your long runs, never for the first time on race day. Dial in what your stomach tolerates and roughly how often you need it, and race day gets a lot less risky.
The taper
In the final one to two weeks you cut back volume while keeping a touch of intensity, letting accumulated fatigue drain so fresh legs meet the start line. Resist the urge to cram: no long run in the last week will make you fitter, but it can absolutely make you tired. Trust the work you've banked.
How Runked's plan works
Training plans in Runked are a PRO feature, included in the 7-day free trial. Choose "train for a race," pick 21.1K half marathon, set your race date and goal time, and the app builds a personalized block around your ability, sessions per week, available days, long-run day and distance, and weekly mileage. The plan is laid out week by week through Foundation, Early Quality, Transition, Race Prep and Taper, with a clear CURRENT WEEK marker so you always know where you are. Life shifts around? Manage Plan lets you edit inputs and regenerate.
Race predictions, also part of PRO, project your finish time for the half and update as your fitness builds, so you can watch your 21.1K readiness improve across the block instead of guessing whether the goal is realistic.
When you get sick or hurt
Sixteen weeks is a long time to stay perfectly healthy. Runked's status selector lets you set Rest, Sick, or Injured to pause the plan, then pick back up as Active when you recover. One disrupted week won't unravel the whole build.
Build your half marathon plan
Runked is free to download, and your rank, GPS tracking and weekly leagues are free forever. Personalized training plans and race predictions are PRO, with a 7-day free trial, so you can build and try your full 21.1K block first.
Download Runked FreeFrequently asked questions
How long do I need to train for a half marathon?
Most runners need 10 to 16 weeks, running 3 to 5 days a week. From a comfortable 10K, 10 to 12 weeks works; building the distance from scratch takes 14 to 16.
Can I train for a half marathon in 8 weeks?
Only with a solid base already — a comfortable 10K and a long run near 8 miles. Eight weeks sharpens existing fitness but is too little to build the distance safely from scratch.
How many miles a week for half marathon training?
Beginners often peak around 20 to 25 miles a week; experienced runners chasing a time reach 30 to 40. The long run anchors it, building toward 10 to 13 miles. Consistency matters more than raw volume.
What pace should my long runs be?
Mostly easy and conversational, around 60 to 90 seconds per mile slower than goal half pace. Later in the block you can add segments at half-marathon pace to rehearse race effort.