The International Association of Athletics Federations set the standard track length at 400 meters, so an individual who travels 300 meters around a track travels three-quarters of the track. The only track and field event that is 300 meters long is the 300-meter hurdles. A person who runs 300 meters runs a distance of approximately 984 feet.
Because few races are 300 meters long, there are some who use the 300-meter mark on a track as a marker to help them keep pace. For example, a person running a 400-meter dash understands that at the 300-meter mark, they only have 100 meters left, so they accelerate into the final phase of the race.