How long is a marathon?

The distance is fixed; the time is not. The middle of the field finishes in about 4 hours 30 minutes — Runsy's synthesis of four published studies covering more than 100 million race results, not a rule of thumb. The table below turns any target finish into the pace it demands and the splits you would have to hit to hold it.

Here is the part a distance page normally leaves out. The race distance is not the number that governs your training — your weekly volume is, and the race distance mostly sets a floor under it.

So rather than describe that in the abstract, here is what Runsy's plan engine actually generates for a beginner with sixteen weeks: three runs a week, no doubles, no track sessions, no cross-training you have to schedule.

The longest run in that plan is 29 km — thirteen kilometres short of the race, and that is deliberate rather than an oversight. It is the standard shape of marathon training at every level, from first-timers to people chasing a qualifying time.

The reasoning is a trade. A 29 km run at genuine easy pace already takes three hours and change, and beyond roughly that point the recovery cost of going further climbs faster than the fitness you get back — you spend the following week too tired to do the training that was supposed to make you faster. Runsy's engine caps the long run where that trade turns, which is the same rule most published plans arrive at.

The last thirteen kilometres on race day are bought with the other 591 in the block, with the taper, and with fuelling — not with one heroic Sunday.

591 km at a genuine easy pace of 6:30 to 7:00 per kilometre is somewhere between 64 and 69 hours of running, spread across four months. That averages a little under four and a half hours a week — less than most people fear and more than most people have spare.

It is not evenly distributed, which is the part worth planning around. Weeks 1 to 3 run 29 to 35 km and fit inside an ordinary life. Weeks 9 to 12 are the pinch: 47 to 52 km each, with a long run of 26 to 29 km that will take most of a weekend morning, every weekend, four weeks running. If there is a fortnight in your calendar that cannot absorb that, put it in weeks 4, 8, or the taper.

If sixteen weeks does not fit, the same engine builds a 20-week version that reaches the same 52 km peak more gradually, and a 12-week version for runners who already have a base. Start from the marathon plans index if you are not sure which level you are.

The first modern Olympic marathon, Athens 1896, was about 40 km — roughly the distance from Marathon to Athens, which is where the name comes from. The distance was not fixed at that point. It drifted between about 40 and 42.75 km from one Games to the next for the following twelve years.

Then London, 1908. The course was laid out from Windsor Castle to the White City Stadium, and — as the story is usually told — the finish was placed in front of the royal box, adding a partial lap of the track to make 26 miles and 385 yards. That is 42.195 km. It was adopted as the official marathon distance in 1921 and has not changed since.

So the answer to "why 26.2 and not 26?" is that one stadium's finish line happened to sit 385 yards past where a 26-mile course would have ended, and the sport standardised on that one course thirteen years later. Nothing about the human body chose it.

The half marathon is exactly half, which makes it the only honest checkpoint on the way — and the reason most marathon blocks put a half-marathon race somewhere in the build. Doubling a half-marathon time and adding ten to twenty minutes is the crude version of a marathon prediction, and it is crude for a real reason: the second half is run on a body that has already used most of its stored carbohydrate.

If you have never raced a marathon, a half-marathon block first is not a detour. It is the fastest route.