Half marathon training plan: how to prepare for 21.1 km

How long does it take to prepare for a half marathon?

Your starting point decides it. If you run a few days a week and can comfortably manage an easy run of close to an hour, two to three months of preparation is common advice. If you cannot yet run 5 or 10 km without interruption, spend a few months building a base at those distances first. Count back from race day and leave a few weeks of margin for illness or busy spells.

The half marathon is the best stepping stone towards a marathon. It teaches the long-run habit, a race-morning routine and pacing discipline at a far lower recovery cost, and most runners are back to normal training within a week. If a marathon is on your horizon, racing a half first tests your preparation and gives you reliable data for a marathon goal time.

How should a half marathon training week be structured?

Most of the week is easy: you can hold a conversation and your legs do not feel heavy the next morning. Two key sessions sit on top of that, the weekend long run and a midweek tempo or threshold workout. Put at least one easy day or rest day between them; stacking hard days back to back reduces what you get from both.

With three running days the layout is simple: one quality session, one easy run, one long run. With four, add another easy run. On five days, finish one of the easy runs with a few short strides. Before adding days, make sure you can keep the days you already have without missing them; that is the safer way to progress.

• Easy runs: most of the week, at conversational pace.
• Long run: once a week, steady and continuous.
• Tempo or threshold session: once a week, controlled but hard.
• Strength: short and regular, for hips, calves and core.
• Rest: at least one day.

How close to the race distance should the long run get?

Unlike the marathon, it is reasonable for most runners to bring the long run close to, or up to, the race distance. The recovery cost is manageable, and covering the distance once at an easy pace builds confidence for race day. The long run grows gradually for a few weeks, then a lighter week with a shorter long run follows. Lengthening it every single week lets fatigue pile up.

Keep most of the long run easy. In the second half of your preparation, running the last few kilometres at goal race pace teaches you to hold pace when tired, the single most useful way to make a long run resemble the race. If you expect to finish in over two hours, practise drinking and taking a gel on long runs too, so you know what your stomach tolerates before race day.

Why tempo and threshold work matter so much for the half

For most runners, half marathon pace sits a little below threshold effort: uncomfortable but controlled, the kind of effort where you can only speak a few words. So anything that lifts your threshold makes your race pace faster. Threshold can be thought of as the highest effort you can sustain without fatigue running away from you; the higher it is, the faster you can hold on.

There are two common forms: a continuous tempo run, or several threshold repeats of a few minutes with short, slow jogs between them. Repeats let you accumulate more total time at the same effort; a continuous tempo feels more like the mental side of racing. One rule applies to both: you should finish feeling you could have done one more. If you are fighting through the last repeat, the pace is too fast.

Setting a goal from your 10K and pacing the race

The best source for a realistic goal is a 10K you have raced in the last few months. Half marathon pace is clearly slower than 10K pace: doubling your 10K time gives an optimistic estimate for most runners, and the realistic time is usually a few minutes slower. Online race-time predictors are a good starting point, but read them more cautiously if your weekly volume is low.

The best strategy in a half marathon is even pacing. In the first kilometres the crowd and adrenaline push you faster than planned; it feels easy at the time and you pay for it over the last five. Run the first few kilometres deliberately a touch slower than goal pace, settle in the middle and open up near the end if you have energy left. A slightly faster second half, a negative split, is common to most good races.

A short taper, race day and common mistakes

The taper for a half marathon is shorter than for a marathon; volume usually comes down over roughly the final week. Intensity does not vanish: a few short sections at goal pace keep your legs sharp. Do not try to gain fitness that week; the best thing you can do is arrive rested. On race morning, eat a breakfast you have tested, warm up with a short easy jog and a few strides, then trust your plan.

The mistakes half marathon runners make are familiar, and nearly all of them can be avoided once you know them. Read this list at the start of your preparation and again in race week.

• Running easy days at a moderate pace and arriving tired at the tempo session.
• Racing the tempo session; controlled hard is enough.
• Picking a goal from hope rather than from a recent 10K.
• Running the first kilometres well faster than goal pace.
• Cramming missed workouts into the following days.
• Running through pain that does not go away; if it persists, see a health professional.

Frequently asked questions