Half Marathon Training Plan: 12 Weeks to 13.1 Miles

13.1 miles (21.1 kilometres) is the perfect distance for your first structured training plan: long enough to demand real endurance, short enough to prepare for properly in twelve weeks. This half marathon training plan explains the complete build — the three phases, the weekly structure with three to four sessions, the key workouts, and the pace targets for finish times from 1:45 to 2:30. Prerequisite: you can currently run 10 kilometres (6.2 miles) in one go and run two to three times per week.

Why 12 weeks is the right length

Shorter plans of six or eight weeks only work for runners with existing fitness — they polish, but they do not build. Longer plans beyond 16 weeks are rarely necessary for the half marathon and increase the risk of losing motivation or freshness. Twelve weeks allow exactly what the body's adaptation needs: three clearly separated training blocks of three to four weeks each, with recovery weeks in between. The physiological adaptations — more mitochondria, better capillarisation, improved running form under fatigue — require repetition over weeks, not intensity over days.

The underlying logic follows the 80/20 principle: around 80 percent of weekly mileage runs easy, only 20 percent hard. Anyone who ignores this split and makes every run "moderate" trains exactly in the zone that makes you tired without making you fast.

Phase 1 (weeks 1–4): Building the base

The first four weeks belong to aerobic base work. All runs happen at an easy, conversational pace — as a rule of thumb, 60 to 75 percent of maximum heart rate. If you train by pulse, the exact boundaries are in the article on heart rate zones. The long run starts at 10 to 12 kilometres (6 to 7.5 miles) and grows by roughly 1.5 to 2 kilometres each week. Weekly volume begins at 20 to 28 kilometres depending on your background and increases by no more than ten percent per week.

The only intensity in this phase: four to six strides of 80 to 100 metres after an easy run, once per week. They train running form and fast-twitch fibres without stressing the metabolism. Week 4 is the first recovery week: cut volume by 30 to 40 percent, the long run drops back to 8 to 10 kilometres.

Phase 2 (weeks 5–8): Building tempo

Now the decisive session arrives: the threshold run. Once per week you run 15 to 25 minutes (later up to 30) at lactate threshold pace — "comfortably hard", a pace you could theoretically hold for an hour. This session raises exactly the threshold that determines your half marathon race pace. The article Threshold Training: Tempo Without Overload explains intensity control in detail — the most common failure point of this phase.

The long run grows to 14 to 18 kilometres in this phase. From week 6, every other week you can run the last 3 to 4 kilometres of the long run at goal race pace — this teaches the body to hold race speed on tired legs. Weekly volume peaks here: 32 to 40 kilometres (20 to 25 miles), depending on your goal time. Week 8 is a recovery week again.

Phase 3 (weeks 9–11): Race-specific work and peak form

The final three weeks before the taper make the difference between "getting round" and "racing the clock". Threshold sessions become more race-like: intervals of 3 x 2,000 metres or 5 x 1,000 metres at 10k pace or slightly faster, with 90 seconds of jogging recovery. The long run peaks in week 9 or 10 at 16 to 18 kilometres — more is unnecessary for the half marathon distance and only raises injury risk.

The most important appointment of this phase: the dress rehearsal in week 10. A 12- to 14-kilometre run in which you cover the middle 6 to 8 kilometres at exactly your planned race pace — including race kit, race breakfast and the gel you intend to use. Anything that niggles here becomes a problem on race day.

Week 12: The taper

In the final week, volume drops by 40 to 50 percent, but intensity stays: two short, sharp sessions with a few repetitions at race pace keep the legs snappy while fatigue drains away. For the half marathon, one taper week is enough — unlike the two to three weeks for the marathon described in Tapering Before Race Day. Anyone who nervously squeezes in "one last long run" throws away the freshness they spent eleven weeks earning.

The weekly structure at a glance

• Monday: Rest day or very light cross-training (swimming, cycling, walking).
• Tuesday: Quality session — threshold run in phase 2, intervals in phase 3; before that, an easy run with strides.
• Wednesday: Rest or 30 minutes very easy.
• Thursday: Easy run, 45 to 60 minutes. Optional: 20 minutes of strength training for runners afterwards.
• Friday: Rest day — the day before the long run stays free.
• Saturday or Sunday: The long run, the fixed anchor of the week.
• Optional fourth session: An additional easy 30- to 40-minute run on Wednesday once weekly volume exceeds 30 kilometres.

Pace targets by goal time

• Goal 2:30 (11:27/mile, 7:06/km): Easy runs 12:30–13:40/mile, threshold 10:28–10:52/mile, intervals 9:23–9:55/mile.
• Goal 2:15 (10:18/mile, 6:24/km): Easy runs 11:16–12:28/mile, threshold 9:31–9:55/mile, intervals 8:35–9:07/mile.
• Goal 2:00 (9:09/mile, 5:41/km): Easy runs 10:04–11:16/mile, threshold 8:27–8:51/mile, intervals 7:38–8:03/mile.
• Goal 1:45 (8:01/mile, 4:59/km): Easy runs 8:51–9:55/mile, threshold 7:23–7:47/mile, intervals 6:42–7:06/mile.

These numbers assume normal conditions — flat course, 50 to 65 °F (10 to 18 °C), little wind. In heat or wind, heart rate outranks pace: anyone who forces the numbers while their pulse sits ten beats above plan is training the wrong zone.

The 6 most common half marathon training mistakes

• Running easy days too fast. The most frequent mistake by far. Easy means: conversational pace, pulse below 75 percent. Anything above eats the recovery your quality sessions depend on.
• Skipping the long run. Missing a week is no drama — but the long run is the one session you must never "make up". Never schedule two long runs back to back as compensation.
• Breaking the 10-percent rule. Volume jumps beyond 10 to 15 percent per week are the main driver of shin splints and Achilles problems.
• Skipping recovery weeks. Every fourth week runs 30 to 40 percent shorter. Adaptation happens during recovery, not under load.
• Anything new on race day. Shoes, gels, breakfast, socks — everything gets tested in training, nothing in the race. The dress rehearsal in week 10 exists exactly for this.
• Starting too fast. Run the first two miles 10 to 15 seconds per mile slower than goal pace — adrenaline lies, and the minute you give away will not come back over 13.1 miles.

And after that? The road to the marathon

If you finish the half marathon under two hours and want to keep growing, you hold the ideal base for the next step: the 16-week marathon training plan builds directly on the structure described here — with longer long runs, two quality sessions per week and an extended taper.

How Peakora builds your half marathon plan

The plan above is a proven framework — but it does not know you. The Peakora engine builds your half marathon training plan from your actual data: current pace, available training days, goal time and race date. Every week is reassessed: were you ill, was the long run too hard, have you become faster than planned — the plan adjusts volume and intensity automatically instead of clinging to paper. Tapering, recovery weeks and the dress rehearsal are built in, and on race day you get pace guidance and a checklist straight to your wrist.

Half marathon training plan FAQ

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

12 weeks is the standard for runners who can already cover 10 kilometres (6.2 miles) in one go. Complete beginners should plan 16 to 20 weeks and build a 10k base first. Anyone regularly running 15 kilometres can get race-ready with 8 weeks of focused preparation.

How many days a week should I run for a half marathon?

Three to four running sessions per week are enough for most goal times. The classic structure: one long run, one tempo or threshold session, and one to two easy runs. More than five sessions add little benefit at this distance but raise the injury risk significantly.

How long should the longest run be in half marathon training?

16 to 18 kilometres (10 to 11 miles). Unlike marathon training, you do not need to come close to race distance in training — total weekly load matters more than one very long run. Runs beyond 20 kilometres raise the injury risk more than they improve half marathon fitness.

Can I run a half marathon with no running experience?

Yes, with enough lead time. Starting from zero, plan 16 to 20 weeks: the first 6 to 8 weeks for run-walk intervals and a 10k base, then the classic 12-week build. Jumping straight into a 12-week plan without any base is the most common cause of injuries and dropouts.