Half Marathon Training Guide — 12-Week Plan for Beginners
A half marathon — 21.0975 km — is the sweet spot of distance running: far enough to demand real training, short enough that a beginner can be ready in twelve weeks. It is also the distance where a plan matters most. Runners who follow a structured twelve-week build arrive at the start line fit and uninjured; runners who wing it arrive tired, or do not arrive at all.
This guide is a twelve-week plan for a beginner who can already run 5 km without stopping. It builds weekly distance gradually, adds one long run a week, includes rest and a taper, and gives pace targets you can calculate for your own goal time.
Use the calculator
Start with the numbers: try our half marathon pace calculator and the pace calculator to work out your own figures before applying anything on this page. The worked examples below use round numbers so you can follow the maths; the calculators use your real weight, height, age and goal.
Related reading: half marathon pace calculator, pace calculator, Running Shoes Guide — How to Choose the Right Pair, What to Eat Before a Workout — Timing and Food Choices. You can also browse the full guides section for the rest of the series.
The key points
The base: can you run 5 km?. Twelve weeks is enough if you can already run 5 km continuously, even slowly. If you cannot, spend four weeks building to that first — run-walk intervals of 1 minute running and 1 minute walking, three times a week, extending the running intervals until 5 km is comfortable. Starting a half-marathon plan before you can run 5 km is the most common cause of injury in beginners, because the weekly distance jumps too fast for tendons and bones to adapt.
The long run is the backbone. One long run a week, building by about 10% a week, is the core of the plan. It starts at 8 km and reaches 16–18 km by week ten. The long run is done slowly — at a pace where you can hold a conversation — because its job is to teach your body to burn fat, spare glycogen and tolerate time on your feet, not to test your speed. If you can only run three days a week, make them: one long run, one easy run, one session with some faster running.
Weekly structure that works. A four-day week looks like this: Tuesday easy run (30–40 minutes), Thursday tempo or intervals (20–30 minutes with faster sections), Saturday long run, Sunday rest or a short recovery jog. Monday, Wednesday and Friday are rest or cross-training — cycling, swimming or strength work. Strength work matters more than most beginners think: two short sessions a week of squats, lunges, calf raises and core work reduce injury risk measurably, and they do not have to be heavy.
Pace: slow is fast. Most beginners run their easy runs too fast and their hard runs too slow. Easy runs should feel genuinely easy — you should be able to talk in full sentences — which for a 2-hour half-marathon goal means roughly 6:30–7:00 per km on easy days. Tempo pace is 'comfortably hard': you can speak in short sentences but not chat. Race pace for a 2-hour finish is 5:41 per km. Use the half marathon pace calculator to work out your own target from your goal time, and do most of your running slower than race pace.
Fuel and hydration on long runs. Runs under 75 minutes need nothing but water. Beyond that, take carbohydrate — roughly 30–60 g per hour, as gels, chews or sports drink — and practise it in training, never for the first time on race day. Drink to thirst plus a little: carrying a bottle on runs over 90 minutes is sensible, and weighing yourself before and after a long run tells you how much fluid you actually lose. A post-run meal with carbohydrate and 20–30 g of protein within a couple of hours covers recovery.
Taper and race week. The last two weeks are a taper: cut weekly distance by about 30% in week eleven and 50% in race week, but keep some short faster running so your legs stay sharp. The fitness is already built — the taper lets fatigue fade so it can show. Race week means normal food (no carb-loading feast needed at this distance, though a slightly higher carbohydrate intake for two days helps), no new shoes, no new foods, and an early night two nights before the race, which matters more than the night before.
At a glance
| Week | Long run | Total weekly distance | Notes |
|---|---|---|---|
| 1 | 8 km | ~20 km | Establish the routine |
| 2 | 9 km | ~22 km | Add 10% |
| 3 | 10 km | ~24 km | First double-digit long run |
| 4 | 8 km | ~20 km | Cut-back week |
| 5 | 11 km | ~26 km | Build resumes |
| 6 | 12 km | ~28 km | Add a tempo session |
| 7 | 14 km | ~30 km | Longest so far |
| 8 | 12 km | ~26 km | Cut-back week |
| 9 | 15 km | ~32 km | Peak build |
| 10 | 16–18 km | ~34 km | Longest run |
| 11 | 12 km | ~24 km | Taper begins |
| 12 | Race: 21.1 km | ~15 km + race | Race week |
Your plan, step by step
- Confirm you can run 5 km continuously; if not, spend 4 weeks building to it first.
- Follow the 12-week plan: one long run a week (+10%), two easy runs, one faster session.
- Add two short strength sessions a week (squats, lunges, calf raises, core).
- Practise race-day fuel on long runs over 75 minutes (30–60 g carbohydrate per hour).
- Taper for two weeks, keep your routine normal in race week, and run the first 5 km slower than goal pace.
The formula behind it
Race pace comes from a simple division: pace per km = goal time ÷ distance. For a half marathon the distance is 21.0975 km.
Worked example — a 2-hour goal: 120 minutes ÷ 21.0975 km = 5.69 minutes per km, or 5:41 per km (5 minutes 41 seconds per kilometre). In miles that is 9:09 per mile. A 2:30 goal gives 150 ÷ 21.0975 = 7.11 minutes per km, or 7:07 per km (11:26 per mile). Use the half marathon pace calculator to work out your own target, then train mostly slower than race pace — easy runs 60–90 seconds per km slower than goal pace, tempo runs at about goal pace or slightly faster.
How to use this guide
The pattern that works is the same for every topic on this page: understand the principle, apply it for two to four weeks, and judge it by what changes — not by how it feels on day one. Most fitness and nutrition advice fails not because it is wrong but because it is applied for three days and then abandoned. Pick the one or two changes from this guide that fit your life, do them consistently for a month, and only then decide whether they are working. If you try to change everything at once, you will not know what helped, and you will not sustain any of it.
Related pages on this site go deeper on the numbers behind this guide: the calculators apply the same formulas shown here to your own weight, height, age and goal, and the protein, macro and body-composition articles work through the maths for specific cases. Use this guide for the understanding and the calculators for your own figures — neither replaces the other.
What this guide does NOT tell you
No guide can replace individual advice. The numbers and ranges on this page are population estimates from published research, and they describe what works on average — your body, your health conditions, your medicines and your training history all shift the answer. This guide does not diagnose anything, prescribe anything, or predict your results. If you have a medical condition (especially heart disease, diabetes, kidney or liver disease, an eating disorder, or a hormone condition), are pregnant, or take prescription medicine, the right next step is a clinician or a registered dietitian, not a more detailed article.
The other limit is honesty about evidence. Some claims in fitness are supported by randomised trials; others are supported by tradition, by a single small study, or by nothing at all. This guide says which is which where it matters, and where the evidence is thin it says so rather than dressing a guess up as a fact. A guide that admits uncertainty is more useful than one that pretends to know everything — and a reader who knows the limits of the advice is safer than one who follows it blindly.
Frequently asked questions
How long does it take to train for a half marathon?
Twelve weeks is enough for a beginner who can already run 5 km. If you are starting from no running at all, allow sixteen to twenty weeks: four to eight weeks to build to 5 km, then the twelve-week plan. Rushing the build is the main cause of injury — tendons and bones adapt more slowly than fitness does, so the plan's gradual 10% weekly increases exist to protect them.
How many days a week should I run?
Three to four days is the sweet spot for beginners: one long run, one or two easy runs, and one session with faster running. More than five days adds injury risk without much benefit at this level, and fewer than three makes the long run too large a share of the week. Two short strength sessions on non-running days complete the week.
What is a good half marathon time for a beginner?
Finishing healthy is the goal the first time. Typical beginner finish times cluster around 2:00–2:30, with 2:00 (5:41 per km) a common first target and 2:30 (7:07 per km) a realistic one for run-walkers. Your second half marathon is where time goals belong — the first is about completing the distance and learning how your body responds.
Should I run the day before the race?
A short, easy 20-minute jog with a few strides the day before is fine and often helps shake out nerves, but it is optional — complete rest is also fine. What matters is not doing anything new: no new shoes, no new foods, no hard session. The fitness is built; the day before is about arriving fresh.
What should I eat on race morning?
Eat a familiar, carbohydrate-rich breakfast 2–3 hours before the start — toast with jam, porridge with banana, or whatever you practised on long-run days — plus water. Avoid high-fibre, high-fat or unfamiliar foods, and do not try a new gel on race day. During the race, take carbohydrate (30–60 g per hour) from about 45–60 minutes in, with water at aid stations.
Estimates only, not medical advice. Minimum safe intakes: 1,200 kcal/day women, 1,500 kcal/day men — consult a healthcare professional before a very-low-calorie diet.