Why the marathon is 42.195 kilometres

The short answer

The marathon is a road running event over 42.195 kilometres, also expressed as 26 miles and 385 yards. Both describe the same distance in different units. Training plans, pace tables and course profiles should use this standard distance unless an event explicitly offers a different distance or category.

Where the distance comes from

Modern road events use the World Athletics discipline definition. You do not need to remember a particular year or race story to understand the distance; what matters is that 42.195 km is a standard, not an approximation. When an article writes "42 km" or "26.2 miles", that is usually shorthand. Pace calculations should still use 42.195 km.

Miles and kilometres should not be mixed casually: runners training by mile pace and runners training by kilometre pace will see different numbers for the same finish time.

How distance affects pace

Pace is time divided by distance. Over 42.195 km:

• A 4:00 finish averages about 5:41 per kilometre.
• A 3:30 finish averages about 4:59 per kilometre.
• A 5:00 finish averages about 7:07 per kilometre.

These are averages only. In a real race, start congestion, aid-station stops, hills and weather make the first and second halves differ. Treat an average as a target to manage, not a demand that every kilometre be identical.

For accurate conversions, use the pace calculator in RunMap Tools: enter distance and time to get both pace and speed.

What it means for training

42.195 km is not simply two half marathons added together. Glycogen, muscle fatigue, hydration rhythm and psychological swings in the later stages all argue for enough long continuous runs in training, plus practice with race-day fuelling and equipment. The details depend on your own base; do not copy someone else's weekly volume.

If you want to understand why easy running makes up much of a training week, read what easy running really means.

Common confusions

• Marathon and half marathon: the half marathon is 21.0975 km, exactly half the standard marathon. They are different events.
• Course distance and GPS distance: a watch track can measure slightly long or short because of signal drift. It does not override the official course distance.
• Ultramarathon: road or trail events longer than the standard marathon are a different category. Marathon pace models do not automatically apply.

Sources and scope

The distance definition follows World Athletics' road running discipline description. The pace examples are arithmetic and are not a training plan or a finish-time promise. It was checked on 2026-10-27.