Marathon Training Plan: Complete Guide

Sixteen to twenty weeks is the standard range, and it's longer than a half marathon plan for a specific physiological reason: the marathon is raced at only 75–80% of VO₂max — much lower intensity than shorter races — but for two to three times the duration. Building the durability to sustain even moderate effort for three-plus hours takes considerably more time than building the speed for a 5K or 10K.

Below fourteen weeks, most runners don't have enough time to safely build a long run to marathon-appropriate distance without violating the 10% weekly mileage rule. Beyond twenty weeks, the plan starts producing diminishing returns — most amateur runners peak in fitness before the extra weeks are up and either plateau or accumulate unnecessary fatigue.

If you have more than twenty weeks before your race, don't start the formal plan early. Spend the extra time building a comfortable easy-running base — three to four runs a week — so you enter week one of the marathon block already aerobically prepared for the volume increase ahead.

Marathon plans carry the highest weekly mileage of any race distance — commonly peaking at 45–70 km (28–43 miles) per week for intermediate runners, compared to roughly 35–55 km for a half marathon. The extra volume exists almost entirely to support long-run durability, not speed.

The long run is the single most important session in a marathon plan. It should increase gradually — respecting the 10% rule — from an early-plan distance of 12–15 km up to a peak of roughly 32–35 km, three weeks before race day. Runners rarely run the full 42.2 km in training; peaking a few kilometres short and trusting the taper and race-day adrenaline to cover the remainder is standard practice, not a shortcut.

Recovery weeks matter more in marathon training than in any other distance, given the higher cumulative volume. Every third or fourth week should drop total mileage by 20–30% — skipping these is the most common way ambitious marathon plans end in injury rather than a finish line.

A marathon plan spends proportionally more time in the base phase and less in the speed phase than a 5K or 10K plan does — the opposite emphasis. Roughly six weeks of base building, five weeks of strength (tempo-focused) work, and only about three weeks of dedicated speed work is a typical split, compared to a 5K plan that's speed-heavy almost throughout.

This isn't because speed doesn't matter for a marathon — it's because the limiting factor for most marathoners isn't top-end speed, it's whether their aerobic system and connective tissue can sustain three-plus hours of continuous loading. Time spent on interval work that a 5K runner needs is better spent, for a marathoner, on additional easy mileage and long-run practice.

This is a representative week from the strength phase of an eighteen-week plan, running five days:

• →Monday: Rest
• →Tuesday: Easy run, 10 km
• →Wednesday: Tempo — 3 km easy, 8 km at threshold effort, 2 km easy
• →Thursday: Easy run, 8 km
• →Friday: Rest
• →Saturday: Rest or easy 5 km shakeout
• →Sunday: Long run, 26 km at easy pace

The marathon taper is the longest of any distance — typically two to three weeks, cutting volume by 40–60% from peak. This is dramatically more than the taper for shorter races, and for good reason: the accumulated fatigue from 16-plus weeks of high mileage takes longer to shed than the fatigue from a shorter block.

In the final two weeks, your last long run should be no more than 16–19 km, done roughly two weeks out. The week of the race itself should be almost entirely easy, short running — the goal is arriving at the start line with fresh legs and full glycogen stores, not fitting in one more confidence-building long effort.

The heavy, sluggish feeling common in the first week of a marathon taper is normal and expected — it's glycogen and fluid replenishment, not a sign of lost fitness. It typically resolves by race week.

Unlike shorter races, the marathon routinely runs past the point where your body's glycogen stores are exhausted — commonly around the 30–32 km mark for underfueled runners, which is exactly the 'wall' many marathoners describe. In-race fueling (carbohydrate gels or equivalent, roughly every 30–45 minutes) isn't optional the way it often is for a half marathon or shorter — see the dedicated guide on marathon fueling and carb-loading for the specifics.

For a first-timer completing a structured sixteen-to-eighteen-week plan, 4:15–5:00 is a common finishing range. Runners with a half marathon time under 1:50 and a completed 16-week block often finish in the 3:45–4:15 range.

As with every distance, the first marathon goal should be a controlled, even-paced finish rather than an aggressive time target — the gap between a well-paced marathon and a badly paced one is often 15–30 minutes, far larger than the gap fitness alone would predict.