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Half marathon guide: how to choose, train for and run 13.1 miles

The half marathon is 13.1 miles, or 21.1 kilometres. It is long enough to need proper training and short enough to fit around a normal working week, which is why it is one of the most popular race distances in the UK.

Is the half marathon right for you?

If you can already run 10 kilometres without stopping, a half marathon is a realistic goal within about three months. If you are newer to running, it is better to build up through a 5K and a 10K first, so that the long runs in a half marathon plan feel like a step up and not a leap. See a GP before starting if you have a health condition.

Most first-time runners finish somewhere between two hours and two hours forty-five minutes. There is more detail on typical times in what is a good finish time.

How to choose a race

Half marathons vary a great deal, and the right one depends on what you want from the day. When you browse events, compare these points:

  • Course profile. A flat road course is the best choice for a first attempt or a fast time. Hilly and trail courses are slower and harder on the legs, but often more scenic.
  • Size. Big city races have crowds, bands and plenty of company at every pace. Small club races are cheaper to reach, easier to park at and less congested at the start.
  • Time of year. Spring and autumn races usually have the kindest weather. A spring race means training through winter, and an autumn race means long runs in summer heat.
  • Cut-off time. Some events reopen roads after a set time. If you expect to run and walk, check the limit before you enter.
  • Travel. An early start a long way from home adds stress. A local race lets you sleep in your own bed.

How long to train

Allow 10 to 12 weeks if you already run regularly, and 14 to 16 weeks if you are building from a 5K base. Three or four runs a week is enough for most people. A typical week includes:

  • one long run, which grows gradually to 10 to 12 miles (16 to 19 kilometres),
  • one or two easy runs at a pace where you can hold a conversation,
  • one faster session, such as a tempo run or intervals, once you have a few weeks of steady running behind you.

Increase the long run by no more than a mile or so each week, and drop back every third or fourth week to recover. Our half marathon training plan sets this out week by week. In the final two weeks, cut the volume and keep a little speed, as described in the tapering guide.

Pacing the distance

The most common mistake is starting too fast. The first three miles should feel almost too easy. A simple approach is to split the race into three parts:

  1. Miles 1 to 4: settle in, run a few seconds per mile slower than your target pace and let the crowd thin out.
  2. Miles 5 to 10: hold target pace and stay relaxed. This is where the race is run.
  3. Miles 11 to 13.1: if you have energy left, use it now.

Work out your target pace with the pace calculator, or use a recent 10K result in the race time predictor to see what is realistic. A printed pace band on your wrist is a useful back-up if your watch loses signal.

Fuel and drink

For a run lasting more than about 90 minutes, most runners benefit from taking on some carbohydrate during the race. Energy gels, chews or sweets all work. Practise with them on your long runs, because race day is not the time to find out that a product upsets your stomach.

Drink to thirst. Most half marathons have water stations every three miles or so, and on a cool day a few mouthfuls at each is plenty. Eat a familiar breakfast two to three hours before the start.

On the day

Arrive at least an hour before the start. Queues for toilets and bag drop are always longer than expected. Wear kit you have trained in, and nothing new. The race day checklist covers what to pack the night before.

Line up in the start area that matches your expected finish time. If you start among faster runners you will be pulled along too quickly, and if you start too far back you will spend the first mile weaving.

After the race

Keep walking for ten minutes after the finish, put on warm layers and eat something within the hour. Take a few easy days before running again. Once you have a half marathon behind you, the natural next questions are whether to run a faster one or to look at the marathon.