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You’ve signed up for a half marathon. Maybe you panicked slightly afterwards. That’s normal. 21.1km — or 13.1 miles — is a real distance, and if your longest recent run is a parkrun or a casual 5K, the gap probably feels enormous. It isn’t insurmountable, but it does require a proper plan and a realistic understanding of what the next three months involve.
This 12-week plan is built for beginners — meaning runners who can currently run for 20–30 minutes continuously, but haven’t raced beyond 5K or 10K before. If you’re starting from zero, 12 weeks isn’t quite enough; you’ll want to spend a few weeks building a base first or consider a couch to 5K programme before coming back here. But if you’ve got some running in your legs and a race booked, this is where to start.
What follows isn’t a plan that assumes you can train six days a week, sleep nine hours, and meal-prep on Sundays. It’s built for real life: three to four runs per week, a long run that builds gradually, and enough flexibility that a missed session doesn’t derail everything.
What you need before week 1
Before you begin, get one thing straight: this plan works best if you can already run 5K without stopping. You don’t need to be fast — finishing in 35–40 minutes is fine. You just need the aerobic base to absorb consistent training without constantly fighting injury or exhaustion.
You’ll also want a decent pair of shoes. Not necessarily expensive ones, but ones that fit properly and have been worn in. New shoes in week 10 are a bad idea. If you’re not sure what you’re running in right now, it’s worth getting gait-assessed at a running shop — free, takes ten minutes, and worth it. For guidance on what to look for, our best running shoes for half marathon training guide covers the key options without the affiliate fluff.
One more honest point: if you’ve had recent niggles — shin pain, heel soreness, knee issues — sort them before week 1, not during week 6. A small problem ignored in week 2 becomes a forced DNS (did not start) by week 10.
How the plan is structured
The plan runs four sessions per week: two easy runs, one slightly harder mid-week run (with some pace variety), and one long run at the weekend. That’s the core structure. If life means you can only manage three runs in a given week, drop one of the easy runs — not the long run.
Here’s the basic weekly pattern:
| Day | Session | What it means |
|---|---|---|
| Monday | Rest or cross-train | Walk, swim, cycle — low impact |
| Tuesday | Easy run (30–45 min) | Conversational pace — you can talk in sentences |
| Thursday | Structured run (30–50 min) | Includes some tempo or fartlek work |
| Saturday | Rest or easy walk | Recovery |
| Sunday | Long run | Slower than easy pace — this is the week’s main session |
Wednesday and Friday are flexible rest or cross-training days. Cross-training here means anything that keeps you moving without the impact load of running — cycling is particularly good for maintaining fitness without stressing your legs.
Your training paces, simplified
Pace confusion is one of the most common reasons beginners either overtrain or undertrain. Here’s a practical guide based on finishing a half marathon in around 2:15–2:45 — a realistic range for a first-timer.
| Run type | Feel | Example pace range |
|---|---|---|
| Easy run | Conversational — you could talk in full sentences | 7:00–8:00/km |
| Long run | Even easier — relaxed, no pushing | 7:30–8:30/km |
| Tempo effort | Comfortably hard — sentences become difficult | 6:00–6:30/km |
| Race pace (target) | Controlled effort, sustainable | 6:20–7:50/km (depending on goal time) |
These are ranges, not rules. If you’re running in heat, at altitude, after a poor night’s sleep, or early in your training, your easy pace will naturally be slower. That’s fine. Run to effort, not to GPS.
The 12-week plan, week by week
Phase 1: Foundation (Weeks 1–4)
The goal here is consistency, not fitness. You’re building the habit and the connective tissue resilience that will protect you later. Keep all runs genuinely easy — resist the urge to push.
- Week 1: Tue 30 min easy / Thu 30 min easy / Sun 8km long run
- Week 2: Tue 30 min easy / Thu 35 min (last 10 min at tempo effort) / Sun 10km long run
- Week 3: Tue 35 min easy / Thu 35 min with 3×5 min tempo / Sun 11km long run
- Week 4: Recovery week — reduce all runs by 30%. Long run back to 8km. Let your body absorb the load.
Phase 2: Build (Weeks 5–8)
Long runs start to matter more here. The Thursday session gets a bit more structured. You’ll probably feel tired by week 7 — that’s expected, not a sign something’s wrong.
- Week 5: Tue 40 min easy / Thu 40 min with fartlek efforts / Sun 13km long run
- Week 6: Tue 40 min easy / Thu 45 min with 4×5 min tempo / Sun 15km long run
- Week 7: Tue 45 min easy / Thu 45 min structured / Sun 16km long run
- Week 8: Recovery week — Long run 12km, easy runs cut back. Sleep more if you can.
Phase 3: Peak and Taper (Weeks 9–12)
You’re now in the sharpening phase. Week 9 and 10 contain your longest runs — this is where your half marathon fitness is made. Weeks 11 and 12 are about arriving fresh at the start line.
- Week 9: Tue 45 min easy / Thu 50 min with race-pace segments / Sun 18km long run
- Week 10: Tue 40 min easy / Thu 45 min easy-moderate / Sun 19–20km long run
- Week 11: Begin taper — Reduce volume by 25%. Long run 14km. Keep a little pace work in Thursday’s session.
- Week 12: Race week — Tuesday 20–25 min easy, Thursday 15 min easy with 4–5 strides. Rest Friday. Race Sunday.
What to do when the plan falls apart
It will fall apart at some point. Work, illness, bad weather, a week where you just can’t face it — these are not failures, they’re just running.
The rule is: if you miss one run, carry on as planned. If you miss a full week, don’t try to cram two weeks into one — just pick up from where you left off and accept you’ll arrive at the start line slightly less prepared than planned. Slightly less prepared still gets you to the finish.
What matters most is protecting the long run. The two easy runs are maintainable; the long run is where your half marathon fitness is built. Research from the American College of Sports Medicine consistently shows that aerobic base training — sustained, progressive long-distance effort — is the primary driver of endurance adaptation in recreational runners. If you have to cut something, cut the mid-week run first.
Fuelling and hydration on long runs
For runs under 75 minutes, water is enough. Once you’re running for longer — from around week 6 onwards — you need to start thinking about carbohydrate intake during the run itself.
A simple rule: take a gel or chews every 45 minutes on runs over 75 minutes. Practise this during training, not on race day. Gels affect people differently — some runners find them fine, others find them nauseating. The only way to know is to test them in training.
On race day itself, most half marathons provide water stations every 3–4km. Don’t skip them, even if you feel fine. Dehydration sets in before you feel thirsty.
The British Nutrition Foundation’s guidance on sports nutrition is worth a read if you want to go deeper on fuelling for endurance events — it’s evidence-based and written for non-scientists.
Injury warning signs you shouldn’t ignore
Some discomfort is normal in training. Sore legs the day after a long run? Fine. A bit of general fatigue in week 7? Expected. But certain signals mean you should stop, not push through:
- Sharp or localised bone pain (especially in shins or feet) — stop and get it checked
- Pain that worsens as you run, rather than easing off after 10 minutes
- Swelling around a joint that doesn’t resolve within 48 hours
- Any heel pain that’s worst first thing in the morning (potential plantar fasciitis)
The 10% rule — don’t increase your weekly mileage by more than 10% in a single week — exists for a reason. This plan is designed to respect it, but if you feel like you’re loading up too fast, it’s always better to repeat a week than to power through into injury.
The honest takeaway
- You need to be able to run 5K before starting this plan. If you’re not there yet, build up first — no shame in that, it just changes your timeline.
- The long run is the most important session each week. If you’re short on time, protect Sunday’s run and trim elsewhere.
- Run your easy runs slowly. Most beginners run their easy days too fast and then have nothing left for the sessions that matter. If you can’t hold a conversation, slow down.
- Recovery weeks in weeks 4 and 8 aren’t optional. They’re where the adaptation actually happens. Skipping them to “do more” is one of the most common beginner mistakes.
- Finishing is the goal. A first half marathon is not about time. Arriving at the start line healthy and leaving the finish line upright — that’s success. If you want to chase a specific time later, there’s always the next step up to marathon distance when you’re ready.
Next read: How long does it take to train for a half marathon?