The marathon distance of 26 miles 385 yards (42.195 kilometers) was set almost by accident at the 1908 London Olympics, then officially adopted as the global standard in 1921. Before that, the marathon had no fixed length. The first seven Olympic marathons used six different distances, ranging from 24.85 miles to 26.56 miles.
The Ancient Legend Behind the Race
The marathon traces its inspiration to the Battle of Marathon in 490 BCE, but the famous story of a Greek soldier sprinting from Marathon to Athens to announce victory and then collapsing dead is almost certainly a myth. The Greek historian Herodotus, who lived close enough to the battle to interview elderly veterans, never mentions anyone running from Marathon to Athens. What Herodotus does describe is a professional long-distance runner named Philippides (sometimes spelled Pheidippides) who was sent from Athens to Sparta to request military help before the battle. That distance was roughly 136 miles, covered in two days. The dramatic 25-mile dash to Athens with news of victory was a later invention, likely embellished by the Roman writer Plutarch centuries after the fact.
The First Olympic Marathon in 1896
When the modern Olympics launched in Athens in 1896, organizers created a race inspired by the Philippides legend. The route ran about 25 miles (40 kilometers) from Marathon Bridge to the Panathenaic Stadium in Athens. There was no particular reason for that exact distance beyond the geography between the two landmarks. It simply covered the ground between the battlefield and the city.
That distance wasn’t treated as sacred. Each host city designed its own course over the next several Olympics, and the length shifted every time. The 1900 Paris marathon measured 25.02 miles. St. Louis in 1904 returned to roughly 24.85 miles. The 1906 Athens games stretched the course to 26.01 miles. No governing body had declared what a marathon should be.
How the 1908 London Olympics Changed Everything
The British Olympic Committee wanted the 1908 marathon to start at Windsor Castle and finish in front of the royal box at the Olympic stadium in London, giving the royal family a prime view of the finish. That specific route happened to measure 26 miles 385 yards. It was a decision driven by royal convenience, not athletic tradition or physiological reasoning.
The race itself produced one of the most dramatic finishes in Olympic history. Italian runner Dorando Pietri entered the stadium first but collapsed repeatedly on the track, was helped across the finish line by officials, and was ultimately disqualified. The spectacle made the 1908 marathon internationally famous, and its distance stuck in public memory far more than any of the earlier, shorter versions.
Thirteen Years of Inconsistency
Even after the drama of 1908, the distance didn’t immediately become standard. The 1912 Stockholm Olympics used a course of just 24.98 miles. The 1920 Antwerp Games went longer than London at 26.56 miles. In total, the first seven Olympic marathons across 24 years used six different distances. The idea that a marathon meant any particular number of miles simply didn’t exist yet.
The 1921 Decision That Set the Standard
In 1921, the International Amateur Athletic Federation (now World Athletics) formally adopted 42.195 kilometers, or 26 miles 385 yards, as the official marathon distance for all future competition. The 1924 Paris Olympics was the first Games to use this standardized measurement, and every Olympic and major marathon since has followed it. The choice of London’s 1908 distance over any of the others was largely a product of that race’s fame and the round-sounding number it produced when converted to metric.
The “26.2” that runners stick on their car bumpers is a rounded figure. The precise distance is 26 miles and 385 yards, which converts to 42.195 kilometers exactly.
How Modern Courses Are Measured
Today, every certified marathon course must measure exactly 42.195 kilometers, and the method used to verify this is surprisingly low-tech. A device called the Jones Counter, invented by a road-race enthusiast who modified a bicycle odometer, has been the standard measurement tool for more than 40 years. The concept is straightforward: a counter attached to a bicycle’s front axle records the precise number of wheel rotations as the cyclist rides the course. Before each measurement, the cyclist rides a pre-measured calibration course to establish exactly how many counter clicks equal one kilometer, accounting for tire pressure, temperature, and road surface.
Courses are actually measured along the shortest possible path a runner could take, following the inside of curves and cutting tangents. World Athletics rules also require a “short course prevention factor,” meaning courses are deliberately measured to be slightly longer than 42.195 kilometers (by about 0.1%) so that even small measurement errors never produce a course that’s too short. A world record set on a course that turns out to be even a few meters short would be invalidated, so this buffer protects both race organizers and athletes.