Half Marathon Training Plan for Beginners: Your First 21K

The half marathon is the perfect distance for a beginner who wants a real challenge. It is not so long that it demands years of preparation, but it is demanding enough that crossing the finish line becomes one of the most satisfying moments of your running life. This 16-week plan will take you from running 5K to covering 21.0975 km safely and with confidence.

Can I Run a Half Marathon as a Beginner?

The short answer is yes, as long as you follow a proper plan and meet the minimum base requirements. A half marathon does not ask you to be an elite athlete or to have been running for years. It does ask for consistency, respect for the plan and patience with the progression. The minimum requirement is being able to run 5K without stopping and having at least 3-4 months of regular running behind you.

If you cannot yet run 5K non-stop, do not jump into this plan. Build that base first with our guide to start running from scratch, and once 5K feels comfortable, come back here.

Prerequisites Before You Start the Plan

Before you begin week 1, check that you tick every one of these boxes:

• Run 5K without stopping: The pace does not matter, only that you can cover 5K in one go without dropping to a walk.
• 3 sessions a week for the last 6 weeks: Your body needs a base of consistency. If you have been running once or twice a week, build that base first.
• No active injuries: Pain in your knees, Achilles, plantar fascia or shins is a signal to stop, not to push. Sort out any niggle before you start.
• A medical check-up if you are over 40 or have any cardiovascular condition: This is not bureaucracy, it is common sense. A stress test costs little and buys a lot of peace of mind.

The 16-Week Plan, Week by Week

The plan is split into four phases: Base (weeks 1-4), Build (weeks 5-8), Volume (weeks 9-12), Peak and Taper (weeks 13-16). Each phase raises the load progressively, with a down week every four weeks.

Easy = Zone 2, conversational pace. Tempo = 20-25 minutes at target race pace. Strides = 20-second accelerations at 90% effort with full recovery. Strength = core, glutes and stability work.

The Key Sessions of the Plan

The long run: the soul of the plan

The long run is the most important session of the week. It is where you build aerobic endurance, teach your body to burn fat as fuel and adapt muscles, tendons and joints to half marathon volume. But there is a golden rule that most beginners break: the long run has to be slow.

The right pace: 60-90 seconds per kilometre slower than your target race pace. If you want to finish the half marathon in 2h15 (6:23/km), your long runs should be at 7:23-8:23/km. It feels very slow, and it is — that is exactly the right intensity.

• Never go past 90 minutes during the Base or Build phase
• Drink every 20 minutes if the run goes beyond 60 minutes
• Take a gel every 45-50 minutes on runs longer than 90 minutes
• Put time before distance — if the plan says 17km and you are at 2h10, stop at 2h

Tempo intervals

Tempo work is the second most important session of the plan. It shows up from week 7 and means holding 20-25 minutes at your target race pace. This session trains your anaerobic threshold and teaches your nervous system to hold the pace you have planned for the half marathon.

How to do it: Warm up for 10 minutes easy, hold target pace for 20-25 minutes, then cool down for 10 minutes. If your goal is 2h15, the tempo is at 6:23/km. For 2h30, 7:06/km. For 2h00, 5:41/km.

Active recovery: the invisible training

Recovery sessions, strength work and rest days are not wasted time — they are where your body absorbs the training and improves. Ignoring recovery is the number one cause of injury in beginners preparing for their first half marathon.

• Foam roller: 10-15 minutes after every session on quads, hamstrings, calves and IT band
• Sleep: 7-9 hours. Growth hormone, which drives muscle repair, is released mainly during deep sleep
• Food: the 30-60 minute window after training — protein plus carbohydrates
• Full rest days: respect them, especially in high-load weeks

Shoes for Your First Half Marathon

The volume in this plan — especially between weeks 9 and 15 — is significant. You need shoes with good cushioning to protect your joints on the weekly long runs. This is not the moment for minimalist shoes or speed trainers.

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Nutrition During Training

Nutrition is the second pillar of the plan — as important as the kilometres. A runner preparing for a half marathon has specific needs that shift with each phase of training.

Base macronutrients

• Carbohydrates (55-65% of calories): Your main racing fuel. Rice, pasta, oats, potato, fruit. Do not cut them — you need full glycogen stores for the long runs.
• Protein (1.4-1.6g/kg of body weight): For a 70kg runner, that is 98g to 112g of protein a day. Chicken, eggs, pulses, Greek yoghurt, tofu. Protein is what repairs the muscle after every session.
• Healthy fats (20-30%): Avocado, nuts, olive oil. Do not cut these either — they are needed for vitamin absorption and hormonal health.

Fuelling during long runs

On any run longer than 60 minutes, your body needs glycogen replacement during the session. The guideline is 30 to 60 grams of carbohydrate per hour of exercise. In practice: one energy gel every 40-45 minutes, or a banana broken into pieces every hour.

For a deeper dive into pre- and post-race nutrition strategy, read our article on carb loading for the marathon and half marathon.

Nutrition on Race Day

Breakfast 2-3 hours before the start

The ideal breakfast before a half marathon is rich in medium-absorption carbohydrates, low in fibre and fat, and easy to digest. Tried and tested options: oats with banana and honey, toast with jam, white rice with fruit compote. Avoid whole milk, fried eggs and any fatty food that slows gastric emptying.

• Amount: 400-600 kcal depending on your size and tolerance
• Hydration beforehand: 500ml of water or sports drink in the 2h before the start
• Never try anything new on race day — use exactly what you practised in training

Gels during the race

You will need two to three gels during the half marathon. The recommended schedule:

• Km 7: first gel — before you start feeling the fatigue
• Km 13-14: second gel — as the effort starts to add up
• Km 18 (optional): third gel if you feel you need a final push

Take your gels with water — never dry and never with a sports drink, because that combination can cause stomach trouble. Practise with the exact gels you will use on race day during your long runs.

The 5 Mistakes That Ruin a First Half Marathon

1. Going out too fast in the first 5 km. The most common mistake and the most costly. Adrenaline, music and the atmosphere make you feel invincible at the start. If you go out 30 seconds per kilometre faster than planned, you will pay for it between km 15 and 21.
2. Not hydrating properly. Plenty of beginners run straight past the aid stations because they feel fine. In a half marathon, by the time you feel thirsty you are already 2% dehydrated, which cuts performance by up to 20%.
3. Not training with the gels you plan to race with. Every body reacts differently to gels. If you try a new brand or flavour on race day, you risk stomach trouble in the closing kilometres. Always practise with the same products.
4. Skipping the taper the week before. Nervous runners often try to squeeze in extra kilometres in race week. That is exactly the opposite of what you should do. The taper is part of the training: let your body arrive rested and with full stores.
5. Not sleeping well in the previous 72 hours. The night before the race matters least — nerves make it hard to sleep and that is normal. What really counts are the two nights before that. Sleep well on Thursday and Friday if the race is on Sunday.

Taper Week

Tapering means cutting volume in the days before the race so your body arrives recovered, with full glycogen stores and a fresh nervous system. Dropping volume by 40-50% is right — but keep the quality sessions so you do not lose your sharpness.

What to Expect on Race Day

A half marathon has a characteristic energy curve, and it helps to know it in advance so you do not get carried away by the emotion of the moment.

• Km 0-7 (Control): Conservative start. 15-20 seconds slower than your target pace. Adrenaline will try to pull you along — resist it.
• Km 7-14 (Rhythm): Take your first gel. Settle into target pace and stay there. You should feel relatively comfortable — if you are already suffering here, adjust the pace.
• Km 14-18 (Depth): Fatigue builds. Second gel at km 13-14. Keep your focus and break the course into small mental segments.
• Km 16-18 (The wall): A wave of exhaustion or a low patch can hit. It is completely normal. Your glycogen stores are running down — if you have a third gel, this is where it goes.
• Km 18-21 (Heart): This is no longer a leg race, it is a head race. Every step takes you closer. The last 3 km are the hardest and the most memorable.

Frequently Asked Questions

Abraham Márquez Rodríguez Founder of CorrerJuntos · Triathlete

Running since 2014 and racing triathlon. He founded CorrerJuntos in 2025 with one simple idea: that no runner should have to train alone.