16-Week Half Marathon Training Plan: Base to Race Day

Running a half marathon is 21.1km (13.1 miles) — roughly four times the distance of a 5K. That gap is real, and you need a plan that closes it without wrecking your legs in the process.

This plan is built for runners who can comfortably finish a 5K and run 3–4 days per week. You don't need to be fast. You don't need a huge aerobic base. You need 16 weeks and the willingness to do the boring runs, not just the long ones.

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Who This Is For

Check all three boxes before you start:

1. You can run a 5K without stopping. You don't need a time goal — just the ability to cover 5km on a given day.
2. You can run at least 3 days per week. Four is better. Two is not enough to build safely.
3. You have 16 weeks until race day. Not 12. Not 10. Sixteen. Rushing this is how people DNF or get injured at km 15 (mile 9).

If you've run a 10K before, even better. This plan will still work — you'll just cruise through the first four weeks.

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The 4 Phases

Phase 1: Base (Weeks 1–4)

This phase is slower than you want it to be. Good.

The goal is to build your aerobic engine and get your legs used to consistent running before you ask anything hard of them. Weekly volume starts around 20–30km (13–18 miles) across three or four runs.

You're not tired after these weeks. That's the point. If you're exhausted in week 3, you started too fast or skipped recovery days.

Phase 2: Build (Weeks 5–10)

This is where the actual training happens. Weekly volume climbs to 40–48km (25–30 miles). Long runs stretch from 13 to 18km (8–11 miles). You add a weekly tempo session — this is where your race fitness comes from.

Weeks 5–10 are the grind weeks. You'll have one or two runs that feel awful. That's not a sign to stop; it's a sign the adaptation is happening. Stick to the plan.

Phase 3: Peak (Weeks 11–13)

Three weeks at your highest volume. Long runs hit 19km (12 miles) — you don't need to run the full 21.1km in training; that's what race day is for. Weekly volume tops out at 51–56km (32–35 miles) for higher-volume runners, around 42–45km (26–28 miles) for those doing three days a week.

Week 13 is your last hard week. Finish it, and the hard part is done.

Phase 4: Taper (Weeks 14–16)

Volume drops by roughly 20–25% each week. You might feel sluggish, tired, or like you're losing fitness. You're not. Your body is consolidating everything you've built.

The taper is not the time to squeeze in extra kilometres "just to be safe." Trust the plan. Rest is training.

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The 3 Weekly Sessions

Every week, regardless of phase, you run three types of sessions. Understanding what each one does keeps you from skipping the wrong ones.

1. Long Run (Easy Pace)

The cornerstone of half marathon training. Once a week, usually on the weekend, you run longer than everything else that week — at a genuinely easy pace.

Easy means you can hold a full conversation. If you're breathing hard, you're going too fast. Most runners run their easy runs 40–60 seconds per km too fast. Slow down.

The long run builds your aerobic base, trains your body to burn fat as fuel, and teaches your legs what it feels like to be on their feet for 90 minutes to 2+ hours.

2. Tempo Run (20–35 Min at Threshold)

This is your one hard session per week. Tempo pace is "comfortably hard" — you can say a few words but not full sentences. It sits right at your lactate threshold, training your body to sustain faster paces without accumulating fatigue too quickly.

Start with 20 minutes in week 5. Work up to 35 minutes by week 12. Bookend it with a 10-minute easy warm-up and cool-down.

Tempo runs are the most skipped session in half marathon training. They're uncomfortable. That discomfort is the whole point.

3. Easy Runs (Why People Skip Them and Why They Matter)

The 6km (4-mile) easy run on Tuesday looks pointless. It's not glamorous. It's not the long run, it's not the tempo — it's just running.

Here's why people skip it: it feels optional. Here's why it's not: these runs build your weekly volume, maintain your aerobic base, and improve your running economy without adding meaningful stress. Skipping them consistently keeps your weekly volume artificially low, which means you arrive at race day under-prepared.

Easy means easy. Resist the urge to turn every run into a workout. Running slow makes you faster over time.

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Sample Weeks

Week 2 (Base Phase)

Weekly total: ~21km (~13 mi)

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Week 7 (Build Phase)

Weekly total: ~37–42km (~23–26 mi)

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Week 12 (Peak Phase)

Weekly total: ~51km (~32 mi)

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Week 15 (Taper Phase)

Weekly total: ~21km (~13 mi)

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Half Marathon Pace: Calculate From Your 5K Time

Your easy pace and race pace are linked to your fitness. Here's a quick reference:

These predictions assume 16 weeks of solid training. If you haven't done the training, add 10–15 minutes to your predicted finish and use that as your target.

On race day, start at your goal pace, not faster. The most common half marathon mistake is going out hard in the first 5km because the crowd energy is electric and your legs feel fresh. You will pay for it at km 16 (mile 10).

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The Week Before the Race

This is not the time to bank extra kilometres. It's not the time to test new gear, try a new pre-run food, or run a "confidence" 13km run.

What actually helps:

• Keep runs short (20–30 min, easy pace) on Tuesday and Thursday
• Stay off your feet as much as possible Thursday–Saturday
• Sleep 8+ hours the two nights before the race — the night before is usually bad due to nerves, so the night two days before matters more
• Hydrate consistently; don't "carb load" the morning of — do it the dinner before
• Lay out your gear Saturday night: shoes, socks, shorts, shirt, bib, safety pins, fuel

What doesn't help:

• Extra kilometres "just to feel ready"
• Skipping sleep to watch a movie about running
• Changing any gear you haven't already trained in

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Race Day: Even Pace vs. Negative Split

For first-timers, even pacing is the goal. Run each kilometre at roughly the same pace. This is harder than it sounds when you feel great at km 6.

A negative split — running the second half faster than the first — is the ideal execution for experienced runners. If you have a time goal and have done the training, plan to run the first 11km about 5–10 seconds per km slower than goal pace, then pick it up in the back half.

For your first half marathon: just survive km 11–16. That stretch is where the race actually starts. If you've paced correctly, km 18–21 will feel hard but manageable. If you went out too fast, km 11–16 will feel like a march of shame.

Practical race day checklist:

• Arrive 60–75 minutes early for parking, bag check, and warm-up
• Eat breakfast 2–3 hours before the start (whatever you've been eating before long runs)
• Bring fuel: one gel per 45 minutes of running, plus water at every aid station
• Don't sprint the last kilometre just because you feel okay — you might not feel okay for the next 48 hours if you do

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Want a Plan Built Around Your Actual Schedule?

This template works, but it's still generic. If you want a 16-week plan that accounts for your specific 5K time, the days you can actually run, and your injury history, generate your free personalized plan.

For a more detailed look at the standard plan structure, see the half marathon training plan overview or, if you've already run a half and want a harder program, check out the intermediate half marathon training plan.

Now go run.