What is the distance of the Olympic marathon?

The Olympic marathon is 42.195 kilometres (26.2 miles). This exact distance is used for the marathon at the Summer Olympics and in officially sanctioned marathon racing worldwide.

The event was inspired by the ancient Greek story of Pheidippides, who supposedly ran from Marathon to Athens after the Greek victory over Persia. The first modern Olympic marathon, held in Athens in 1896, was roughly 40 kilometres long rather than today’s fixed distance.

The modern length came from the 1908 London Olympics. Organizers planned a 26-mile course from Windsor Castle to the stadium, then added 385 yards so the race would finish in front of the royal box. That produced 26 miles and 385 yards, or 42.195 kilometres.

The distance was formally standardized in 1921. A common mix-up is treating 26.2 miles and 42.195 kilometres as different answers: they are rounded versions of the same marathon distance. Early Olympic marathons varied because organizers used different courses.