A marathon is a road race covering 42.195 kilometres, or 26.2 miles. It's the longest standard race distance most runners train for, and finishing one is widely treated as a major running milestone.
A marathon is exactly 42.195 kilometres, or 26.2 miles. This distance has been the standard since 1921, when it was formally fixed by what is now World Athletics.
It traces back to the legend of a Greek messenger running from the town of Marathon to Athens. The modern distance was set at the 1908 London Olympics, extended slightly so the race could finish in front of the royal box.
Most recreational runners finish between 4 and 6 hours. Competitive runners can finish under 3 hours, while a run-walk approach often takes 6 to 7 hours, still within most race cutoffs.
Most marathons set a cutoff between 6 and 7 hours, enforced mainly because roads closed for the race need to reopen to traffic. Always check the specific event's stated cutoff rather than assuming.
A marathon is exactly double a half marathon's distance, 42.195 km versus 21.0975 km. It also demands a longer training block, more deliberate pacing and fuelling, and a longer taper before race day.