One hundred meters is a quarter of a lap. A standard running track is 400 meters and is usually divided into eight to ten different lanes. In many countries, the full-lap, 400-meter race started as the now-obsolete 440-yard dash, which is a distance of 402.336 meters.
According to the International Association of Athletics Federations guidelines, the standard track lane width is 48 inches. Each athlete stays in his lane, which is carefully designed to measure 400 meters. Outer lanes include extra distance due to greater radii of turns around corners. For this reason, the starting positions for a full-lap race are staggered, with outer lanes being placed ahead. The distance by which the starting position of each lane is placed ahead is exactly equal to the extra distance it carries.