What is the length of a marathon in miles?

The length of a marathon is officially recognized as 26.2 miles. This measurement has been standardized and is recognized internationally for marathon races. The distance originates from the 1908 London Marathon, which was adjusted to allow the race to start at Windsor Castle and finish at the Olympic Stadium, resulting in the 26.2-mile length.

This specific distance has since become the standard for marathon events around the world, making 26.2 miles the correct and definitive answer to the question about the length of a marathon. Knowing this specific measurement is essential for understanding the context of distance running and race regulations.