12-week half marathon training plan for 10K runners

The half marathon (21.1 km) is a great next goal after 10K: challenging, but without the training hours of a full marathon. This half marathon training plan is for runners who can already run about 10 km continuously, with four sessions a week for 12 weeks.

Before you start

• You can run 8 to 10 km continuously without pain.
• You have been running about three times a week for the last few months.
• You have a pair of broken-in running shoes in good condition.

If not, spend a few more weeks at 5 to 10 km first, or start with the 5K plan.

Four types of run each week

• Easy runs (two): conversational pace.
• Quality run (one): stretches at half marathon goal pace or short faster repeats.
• Long run (one, at the weekend): slow, building distance.
• Add one or two short strength sessions and some stretching if you have time.

The 12-week schedule (weekend long run)

Your two easy runs each week are around 5 to 8 km. Weeks 4 and 8 are lighter so your body can recover. If you are ill or injured, skip the session; do not try to make it up.

Setting your goal pace

Take a recent 10K time and enter it into the pace calculator to see a Riegel-based half marathon prediction. A one-hour 10K, for example, predicts about 2:12. For your first half, aim a little slower than the prediction. To break two hours you need to average just under 5:41 per km.

Long runs: slow is right

Your long run should be clearly slower than goal pace. The aim is endurance, not racing yourself every weekend. It is also the time to practise drinking, test gels, and try the running belt and clothes you will race in.

Race week and race day

In week 12, cut your mileage, sleep well and eat a bit more carbohydrate than usual for two days before the race. On race morning, eat something familiar, arrive early, and run the first 2 to 3 km a little slower than goal pace before settling in. Try nothing new.

Signs to stop

Pain that builds in one spot (shin, knee, heel), pain that changes how you run, or tiredness that lasts for days are signals to rest. Chest pain, dizziness or unusual breathlessness mean stop immediately and see a doctor.

Eating and sleeping through the 12 weeks

As your mileage rises, your body needs more energy to recover. Eat proper meals with carbohydrate, protein and vegetables, and have a meal with both carbs and protein within a few hours of your long run. Drink steadily through the day, especially in hot weather. Sleep is the most underrated part of training: short nights make sessions feel harder and slow your recovery. If you feel tired for days on end, drop one session that week rather than forcing yourself to follow the schedule exactly. A plan is a guide, and the runner who arrives healthy at the start line usually beats the one who trained harder but got hurt.