how many km in a marathon

A marathon is 42.195 kilometers (km) long. This distance is equivalent to 26 miles and 385 yards, or about 26.2 miles. The official marathon distance was standardized at 42.195 km in 1921, based on the length used in the 1908 London Olympic Games. Before that, marathon distances varied but were generally close to 40 km, inspired by the ancient Greek run from Marathon to Athens.