What is the length of one lap on a standard outdoor athletics track?

One lap on a standard outdoor athletics track is 400 metres long.

The 400-metre circuit is measured along the inside edge of the innermost lane. Standard tracks generally have oval shapes with two straights and two semicircular bends, although exact construction details can vary. Races such as the 400 metres and 4 × 400 metres relay are built around this distance.

Because outer lanes follow wider curves, athletes starting in separate lanes must be staggered so that each competitor covers the same total distance. The stagger is calculated from lane measurements and the runner’s position on the track, not simply from the visible starting line.

Indoor tracks are commonly 200 metres per lap, which is why indoor race times and tactics differ from outdoor performances. The older imperial distance of 440 yards is close to, but not identical with, 400 metres; 400 metres equals about 437.45 yards.