Marathon Training Guide — 16-Week Plan, Pacing and Fuelling
A marathon is 42.195 kilometres of running, and it is the distance that humbles everyone who underestimates it — including experienced runners. It is not simply a longer half marathon: the last 10 kilometres are a different event, governed by glycogen, hydration and the accumulated fatigue of three hours on your feet. Finishing strong requires a plan that respects that.
This guide is the 16-week plan: the weekly structure, the long runs that build the endurance, the tempo and interval sessions that add speed, the fuelling strategy that prevents the wall, and the race-day pacing that gets you to the finish in the time you trained for. It assumes you can already run 10K comfortably and have been running regularly for several months.
Use the calculator
Start with your own numbers: try our marathon pace calculator, running calorie calculator to work out your 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 Training Guide — 12-Week Plan for Beginners, Long Runs Explained — How Long, How Slow, How Often, Running Nutrition Guide — What to Eat Before, During and After. You can also browse the full guides section for the rest of the series.
The key points
Sixteen weeks is the standard build. The plan has three phases: base building (weeks 1–6, easy mileage and one long run a week), specific training (weeks 7–13, tempo runs, marathon-pace sessions and the longest runs), and the taper (weeks 14–16, volume falling while sharpness is kept). Rushing the build — a 10-week plan from a low base — is the most common cause of marathon injury and failure.
The long run is the heart of the plan. One run a week, building from 90 minutes to 2.5–3.5 hours, peaking at 30–35 km three weeks before the race. The long run teaches the body to burn fat efficiently, strengthens the legs for hours of impact, and — just as importantly — teaches you to eat and drink while running. Never run the long run fast: it is always at a conversational pace, 45–60 seconds per kilometre slower than marathon pace.
Marathon-pace sessions bridge the gap. From week 7 onward, include sections of the long run at goal marathon pace — 8 km at pace inside a 25 km run, building to 15 km at pace inside a 32 km run. These sessions teach the body what race pace feels like when tired, which is the skill the last 10 km demands. They are the most specific sessions in the plan, and the most revealing: if you cannot hold pace in training, the goal is too ambitious.
Fuelling is a skill to practise, not a race-day improvisation. The body stores about 2,000 kcal of glycogen — enough for roughly 30 km of running — and the marathon is 42 km, which is why the wall exists. The fix is carbohydrate during the race: 30–60 g per hour from gels or drinks, starting from the first hour, plus water at every station. Practise the exact products in training, on the long runs, so race day holds no surprises.
The wall is a fuelling failure, not a fitness failure. Hitting the wall at 30–35 km — legs turning to lead, pace collapsing, the mind fogging — is almost always glycogen depletion, and it is preventable: a proper carbohydrate load in the final days, gels from the first hour, and a pace that respects the distance. Runners who fuel properly and pace evenly rarely hit the wall; runners who skip gels and start too fast almost always do.
The taper is when the fitness arrives. The final three weeks cut volume by 20–40% a week while keeping some intensity, and the body supercompensates: glycogen stores fill, muscle damage repairs, and freshness returns. The taper feels wrong — restless legs, phantom niggles, the urge to run more — and it is right. Trust it: the fitness was built in the previous 13 weeks, and the taper is when it becomes available.
At a glance
| Phase | Weeks | Weekly running | Long run | Key sessions |
|---|---|---|---|---|
| Base | 1–6 | 4–5 hours | 90 min → 2 hours | Easy runs + strides |
| Specific | 7–10 | 5–6 hours | 2–2.5 hours | Tempo + marathon-pace sections |
| Peak | 11–13 | 6–7 hours | 2.5–3.5 hours (30–35 km) | Longest runs + race-pace work |
| Taper | 14–16 | Falling 40% → 70% | 90 min → 60 min | Short, sharp sessions |
Total weekly running for a first marathon is typically 40–60 km; experienced runners may reach 70–90 km. More is not automatically better — the plan must fit your life and your recovery.
The formula behind it
The pacing maths starts with the goal: pace per kilometre = target time ÷ 42.195. A 4-hour marathon needs 240 ÷ 42.195 ≈ 5:41 per kilometre; a 3:30 marathon needs 210 ÷ 42.195 ≈ 4:59 per kilometre; a 5-hour marathon needs 300 ÷ 42.195 ≈ 7:07 per kilometre. To convert to miles, multiply by 1.609: 5:41 per km is about 9:09 per mile.
The Riegel formula (Riegel, 1981) predicts your marathon from a half marathon: time₂ = time₁ × (distance₂ ÷ distance₁)^1.06. A 2-hour half marathon predicts a marathon of 120 × (42.195 ÷ 21.0975)^1.06 = 120 × 2^1.06 ≈ 250.8 minutes — about 4:11. That prediction assumes equivalent training; a runner who has not done the long runs will be slower, because the marathon punishes missing endurance far more than the half does. The calorie maths is the Compendium (Ainsworth et al., 2011): running at 6 mph (9.8 MET) burns 9.8 × weight (kg) per hour, so a 4-hour marathon at 75 kg burns about 2,940 kcal — which is why fuelling during the race is not optional, and why the body cannot finish on stored glycogen alone.
Your plan, step by step
- Build a base first: run 10K comfortably and train 3–4 times a week for at least 2–3 months before starting the 16 weeks.
- Follow the three phases — base, specific, taper — with one long run a week, building by no more than 10% at a time.
- Add a weekly tempo run and marathon-pace sections inside the long run from week 7 onward.
- Practise fuelling on every long run: 30–60 g of carbohydrate per hour, plus water, using the products you will use on race day.
- Taper for three weeks, race with even pacing, and take gels from the first hour — not when you already feel empty.
How to use this guide
Use this guide as a framework and your long runs as the truth. If the 30 km run feels strong and the marathon-pace sections are comfortable, the goal is right. If the long runs are a struggle and the pace sections fall apart, the goal is too ambitious — adjust it now, in training, rather than discovering it at kilometre 32 on race day. The marathon rewards honesty in training and punishes optimism on the day.
Respect the distance in the final weeks: sleep well, eat well, avoid new foods, new shoes and new routines in race week, and arrive at the start line rested rather than over-trained. The marathon is long enough for small problems to become large ones, and the preparation that matters most in the final week is the preparation you do not do — no extra long run, no new supplement, no sudden change.
What this guide does NOT tell you
A marathon is a major physical undertaking, and this guide cannot judge whether it is safe for you: anyone with a heart condition, joint problems, high blood pressure, diabetes, asthma or any medical condition should get a clinician's clearance before starting marathon training, and the training itself should be built gradually from an established running base. Chest pain, severe breathlessness, dizziness, collapse or sharp joint pain are signals to stop immediately and seek help — not to push through.
The paces, volumes and predictions here are population averages: your marathon time depends on your fitness, age, training history, the course and the weather, and the Riegel prediction is an estimate, not a guarantee. This guide is general information, not medical advice, and the 16-week plan assumes a base of regular running — starting a marathon plan from no running at all is not realistic or safe.
Frequently asked questions
How long does it take to train for a marathon?
Sixteen weeks from an established base — meaning you can already run 10K comfortably and have been running 3–4 times a week for a few months. Building the base itself takes another 2–3 months, so the full journey from beginner to marathon is typically 6–9 months. Shorter plans exist, but they carry a much higher risk of injury and of hitting the wall, because the long runs are what prepare the body for 42 km.
What is the wall in a marathon?
The wall is glycogen depletion: the body stores about 2,000 kcal of glycogen, enough for roughly 30 km of running, and when it runs out the legs feel heavy, the pace collapses and thinking gets foggy. It is preventable — carbohydrate loading before the race, gels or drinks providing 30–60 g of carbohydrate per hour from the first hour, and even pacing all reduce the risk sharply. Runners who fuel properly and pace evenly rarely hit the wall.
How many kilometres a week should I run for a marathon?
A first marathon is usually built on 40–60 km a week, with one long run of 25–35 km at the peak; experienced runners may reach 70–90 km. More mileage helps, but only if the body recovers from it — a 50 km week done consistently beats an 80 km week that ends in injury. The long run matters more than the total: a plan with a proper long run and modest total mileage outperforms a plan with high mileage and no long run.
What should I eat during a marathon?
Carbohydrate, little and often: 30–60 g per hour from gels, chews or sports drinks, starting in the first hour — not when you already feel empty. Drink water at every station, and take salt or electrolytes in warm weather. Practise the exact products on your long runs, because the gut needs training too: a gel that works in training is safe on race day, and a new product on race day is a gamble with your stomach.
Should I run the whole marathon or take walk breaks?
Both are legitimate strategies, and walk breaks are not failure: planned run-walk (for example, running 9 minutes and walking 1) helps many first-time marathoners finish strong, with a total time often close to continuous running, because the walking lets the legs recover and makes fuelling easier. If your goal is simply to finish, a run-walk plan is a sensible, proven approach. If your goal is a time, continuous running with even pacing is the faster route — but only if the training supports it.
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.