Marathon training plan: how to build 16–20 weeks of training

A marathon is 42.195 km, or 26.2 miles, and the training for it follows a surprisingly consistent logic across good coaches: build the aerobic engine with lots of easy running, extend the long run step by step, add race-specific work in the final two months, then reduce volume so the body can absorb everything. The guide below explains that structure, gives ranges rather than a one-size-fits-all schedule and shows the pace and fueling numbers with the arithmetic spelled out.

This is general training information, not medical advice. Get a medical check before marathon training if you have heart, lung or metabolic conditions, or if you are new to endurance exercise.

Before you start: are you ready?

Most 16–20 week plans assume you can already run 30–45 minutes continuously, three to four times a week, without pain. If that is not you yet, follow a base-building plan first; our beginner 5K plan is a good starting point. Many coaches suggest a year of consistent running, and a half marathon finish, before a first marathon.

Pick a race 16–20 weeks away. London (April) and the big US autumn races such as Chicago and New York have huge fields; smaller flat races are often kinder for a first attempt.

The four training phases

A 16-week plan shortens the base; a 20-week plan lengthens it or adds a recovery week every third or fourth week. Recovery weeks (volume down by about 20–30%) are worth keeping in any version.

Weekly mileage and long run progression

Weekly volume depends far more on your history than on your goal time. Typical ranges at the peak:

The long run usually grows by 1.5–3 km (1–2 miles) per week, with a shorter long run in recovery weeks. A sample progression for an intermediate runner: 16, 18, 20, 16, 22, 24, 26, 20, 28, 30, 24, 32, 28, 32, then taper long runs of 24 and 16 km before race day. Keep the long run to roughly 30–35% of weekly volume and cap it around 3 hours; beyond that, fatigue rises faster than fitness.

Intensity: the 80/20 principle

Studies of endurance athletes, popularised by physiologist Stephen Seiler, show that well-trained runners do about 80% of their training at low intensity and about 20% at moderate to high intensity. For a recreational marathoner that means:

• Easy runs in zone 2 (talk test passes), the majority of the week.
• One quality session: tempo runs (20–40 minutes “comfortably hard”) or intervals such as 5 × 1 km at threshold.
• Marathon-pace work in the peak phase, e.g. a 28 km long run with the final 10–12 km at goal pace.

Use the heart rate zone calculator to set your easy and threshold zones, and our heart rate zones guide explains the methods.

Goal pace and race prediction

Goal pace is simply goal time divided by distance. The table rounds down so that holding the listed pace gets you under the target:

Worked example: 240 minutes ÷ 42.195 km = 5.688 min, i.e. 5 minutes and 41 seconds per km. Check: 5:41 × 42.195 = 341 s × 42.195 = 14,388 s = 3:59:48. Run any combination with the pace calculator.

To check whether a goal is realistic, use a recent race and the Riegel formula (Riegel, 1981): T2 = T1 × (D2 / D1)^1.06. A 50:00 10K predicts 50 × 4.2195^1.06 ≈ 230 minutes, about 3:50 for the marathon. A 1:55 half predicts roughly 3:59:46. These predictions assume marathon-specific training; with low mileage, real marathon times are usually slower. Try it in the race time predictor, and if you know your VO2max estimate, the VO2max calculator gives another reference point.

Fueling and hydration

Your body stores enough glycogen for roughly 90–120 minutes of hard running, so marathoners need carbohydrate during the race.

• During the race: the ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada joint position stand (2016) recommends 30–60 g of carbohydrate per hour for 1–2.5 hour efforts and up to 90 g per hour for longer ones; the IOC consensus on sports nutrition and the ISSN position stands support the same ranges. Above 60 g per hour, glucose–fructose mixes are absorbed better.
• Gut training: practise race fueling in at least four to six long runs. A typical gel has 20–30 g of carbohydrate, so 60 g per hour means two to three gels per hour.
• Carb loading: 10–12 g of carbohydrate per kg of body weight per day for 36–48 hours before the race (ACSM 2016).
• Fluids: drink to thirst, aiming roughly for 400–800 ml per hour depending on heat and body size, and include sodium. Avoid drinking so much that you gain weight during the race.

The taper and race day

A meta-analysis by Bosquet and colleagues (2007) found that the best tapers last about two weeks and reduce training volume by 41–60% while keeping intensity. Most marathon plans use two to three weeks: cut volume about 20–30% three weeks out, 40% two weeks out and 50–60% in race week, keeping a few short marathon-pace efforts. Feeling restless, heavy or slightly irritable during a taper is normal.

Race week and race day

• Do not try anything new: shoes, breakfast, gels and kit should all be tested.
• Start 5–10 seconds per km slower than goal pace for the first 5 km; crowded starts make this easy.
• Expect your GPS to read long; aim to run the tangents.
• Split the race into three parts: first 21 km controlled, 21–32 km focused, last 10 km all you have.

Sources

• Thomas D.T., Erdman K.A., Burke L.M. (2016): ACSM/AND/DC position stand on nutrition and athletic performance.
• IOC consensus statement on sports nutrition (2011) and ISSN position stands on nutrient timing (2017).
• Bosquet L. et al. (2007), Medicine & Science in Sports & Exercise: effects of tapering on performance – meta-analysis.
• Riegel P.S. (1981), American Scientist: athletic records and human endurance.
• Seiler S. (2010), International Journal of Sports Physiology and Performance: training intensity distribution in endurance athletes.