12-Week Half Marathon Training Plan for Beginners (UK Guide, 2026)

A half marathon is 13.1 miles, or 21.1 kilometres. It is the most popular long distance race in the UK because it is hard enough to feel like a real achievement, but short enough that you can train for it around a job, kids and a normal life. You do not need to give up your weekends or grind out 50 mile weeks. You just need a sensible plan and the discipline to follow it.

This is that plan. Twelve weeks, three runs a week, a long run that builds from 4 miles to 11 miles, then a two week taper into race day. It is built for someone who can already run 5K continuously and who has not been injured in the last few months. If that sounds like you, this plan will get you across the finish line.

We are also going to be honest about what works and what does not. Most beginner half marathon plans add junk miles to look impressive. This one does not. Every run has a purpose. Easy runs build aerobic base. Quality days sharpen pace. The long run teaches your legs to keep moving when they are tired. That is the whole game.

If you would rather skip the printable PDF and have a plan that adjusts to your real starting fitness, Edge builds the same structure around your 5K pace and lets you Flexi Swap sessions when work blows up. But the plan below works on its own. Print it. Stick it on the fridge. Tick the boxes.

Who this plan is for

This plan assumes you can already run 5K (3.1 miles) without stopping, at any pace. If you cannot yet, spend 4 to 6 weeks getting there first. There are simpler couch to 5K plans for that. Trying to jump straight into half marathon training from zero is the fastest route to a stress fracture and a binned race entry fee.

It also assumes you are injury free right now. Niggles in the knees, hips, shins or feet that have been there for weeks need attention before you add training load. See a physio. Get the boring rehab work done. Two weeks of fixing a problem is better than twelve weeks of running through it and ending up unable to start the race.

Finally, you need 4 to 5 hours per week. Three runs ranging from 30 minutes to about 2 hours, plus two short strength sessions, plus warm up and cool down time. If that does not fit your life right now, pick a race further out and use a 16 week plan instead. There is no prize for choosing the most aggressive timeline.

Plan structure explained

Every week of this plan has the same three runs, in roughly the same order. The mileage and intensity change, but the shape stays the same. Once you understand the four building blocks below, you understand the entire plan.

1. Easy runs (60-70% of your weekly mileage)

Easy runs are run at a pace where you can hold a full conversation. If you cannot speak in complete sentences, you are running too fast. This is the most common mistake beginners make. Easy runs are not slow runs you do as punishment. They are the foundation. Your aerobic engine grows during easy miles, not during hard intervals. Most weeks, your easy and long runs together should be around two thirds of your total mileage.

2. Quality day (tempo or intervals)

One run a week is the hard one. Early in the plan this is a tempo run (a sustained block at "comfortably hard" pace, roughly your current 10K race pace). Later, this rotates with interval sessions (faster bursts at 5K pace with short recoveries). The quality day teaches your body to clear lactate faster and run efficiently when tired. It is short, but it earns its place.

3. Long run (the most important session)

The long run is the single most important session every week. It builds the specific endurance you need to keep running for 2 hours plus on race day. It is run at an easy, conversational pace. It is always your longest run of the week, and it is non negotiable. If you can only fit two runs in a busy week, you do the long run and one other. Never skip the long run.

4. Strength (2x per week, 20-30 minutes)

Strength training is not optional if you want to stay injury free. Twice a week, 20 to 30 minutes. Focus on the glutes, hips and calves. This is the work that prevents the runner's knee and the dodgy IT band that ends most beginner training blocks. Do it in your living room. No gym required.

The full 12-week plan

Pace targets are explained in the next section. "Easy" means conversational, "tempo" means comfortably hard (about 10K pace), "5K pace" means the pace you could currently race a 5K at, and "half marathon pace" is the pace you are targeting for race day.

Notice that weeks 4 and 7 are recovery weeks. The long run drops back to give your body a chance to absorb the work. This is not optional. Skipping the down weeks is how beginners end up overtrained by week 9 and pulling out at week 11.

Pace targets for this plan

Pacing is the difference between a successful training block and a stress reaction. If you run easy runs too hard, you cannot run the long run well. If you run the long run too hard, you cannot run the quality day. Beginners almost always run easy too fast and the quality day too slow. Reverse it.

The reference table below gives rough pace ranges based on your current 5K time. These are estimates for guidance, not targets to hit to the second. If you are running on hills, in heat, or feeling tired, slow down and trust the effort. Pace is a tool. Effort is the truth.

Target half marathon pace for a beginner is usually 30 to 45 seconds per mile slower than your current 10K pace. If you do not have a recent 10K time, expect to race the half at roughly your tempo pace from the table above. Do not try to negative split your first half. Aim for even effort, even pace, and finish strong.

How to run the long run

The long run is run slow. Slower than you think. If your easy pace is 11 minutes per mile, your long run might be 11:30 or 12:00 per mile, especially early in the plan. You should be able to talk in complete sentences the whole way. If you are gasping by mile 5, you are running too fast. Back off.

The point of the long run is time on feet, not speed. You are teaching your body to burn fat efficiently, you are teaching your tendons and joints to handle repetitive impact for hours, and you are teaching your brain that running for a long time is something you can do. None of that requires going fast. Going fast on the long run is how people get hurt.

Walk breaks are fine. They are not a sign of failure. Many strong beginner runners use a structured run walk approach (for example, 8 minutes running, 1 minute walking) all the way through their long runs and on race day. If walk breaks let you finish the session feeling good rather than wrecked, use them. The plan still works.

Strength training during the plan

Two short strength sessions per week, ideally on days you do not run hard. Twenty minutes is enough. The goal is not to get strong in the gym sense. The goal is to keep your hips, glutes and calves capable of absorbing impact mile after mile. Without this, the long runs and the increasing mileage will eventually find a weak link and break it.

You do not need equipment. The five exercises below cover the muscle groups that matter most for runners. Do 2 to 3 sets of each, 10 to 15 reps per side. Add a few minutes of hip mobility at the end. That is the whole session.

• Glute bridges. Wakes up the glutes, which most desk workers cannot fire properly.
• Single-leg squats (or pistol progressions). Exposes side to side imbalances before they cause injury.
• Planks (front and side). Core stability that keeps your form from collapsing in the late miles.
• Calf raises (both feet, then single leg). Bulletproofs the Achilles, the most common beginner injury site.
• Side leg raises (clamshells, banded walks). Strengthens hip abductors, prevents the knee falling inward.

Half marathon training is a slow build of capacity. The week that feels too easy is the week the plan is working.

The taper (weeks 11-12)

The taper is the final 10 to 14 days before race day, where you cut volume but keep some intensity. In this plan, the taper begins after the peak long run in week 10. Week 11 drops the long run from 11 miles to 7. Week 12 drops mileage further, keeps one short quality session to keep the legs sharp, and then race day.

The single biggest mistake in the taper is panic training. You feel rested. You feel guilty for not running enough. You sneak in extra miles, decide to test your pace on a Wednesday run, or join friends for a long Sunday "just for fun". Do not do this. Every extra mile in the taper adds zero fitness and risks fresh injury. The fitness is already in the bank. You are letting it surface.

What to do instead: sleep more (an extra 30 to 60 minutes a night if you can), eat normally (this is not the week to try a new diet), stay hydrated, do gentle mobility work, and start visualising the race. Your job is to arrive at the start line fresh and a little bit twitchy. That nervous energy is what you spend in the first mile.

Race week and race day

From the Thursday before race day, start gently increasing your carb intake. You are not loading up on plates of pasta the night before, you are bumping carbs to around 60 to 70% of calories for 2 to 3 days. Hydrate steadily through the week with water and a pinch of electrolytes. Avoid alcohol from Friday onwards. Lay your kit out Saturday night: vest, shorts, socks, shoes, gels, race number safety pinned on, watch charged.

Race morning: wake 3 hours before the start. Eat the breakfast you have practised on long runs: porridge, banana, a slice of toast with jam, a coffee. Do not try anything new. Arrive 60 minutes early to give yourself time for the toilet queue (there is always a toilet queue), bag drop, warm up jog and getting to your start pen.

During the race, take a gel every 30 minutes from mile 4 onwards, sip at every water station, and run the first 3 miles slower than you think you should. The race begins at mile 9, not mile 1. If you feel great at mile 10, you can push. If you do not, hang on, keep your form, and grind it out. You only need to finish once to be a half marathon runner forever.

How Edge fits this plan

The plan above is a solid printable. It will get you across the line if you follow it. What it cannot do is adjust the starting mileage to your real fitness, swap a session when you have a 7am meeting, or remind you to do your strength work. That is what Edge is for. You set your race date, your current 5K time, and the days you can run. Edge builds your starting plan around that and you take it from there.

When life happens, Flexi Swap lets you move a long run from Sunday to Saturday or push a quality day back a day. Strength and mobility sessions are built in with coach video demos so you are not guessing. Sync to Strava, Garmin, Apple Watch or Coros and your runs log automatically against the plan. Need a quick question answered between sessions? Edge AI answers in about 30 seconds when you ask.

Edge has more than 17,000 UK members training this way. There is a free 7 day trial so you can build your half marathon plan, see the first week, and decide. After that it is £19.99 monthly or £119.99 yearly. Cancel any time. If the printable plan above is what you need, brilliant. Print it and crack on. If you want the same structure adapted to your real life, that is what Edge does.

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