Most races break down their race length based on duration of time, rather than distance since the percentage of each discipline in a race can vary dramatically, thus effecting length of the duration. The primary race durations are broken down into three basic categories:

• Short or Sprint Length
  These races usually last from 2 to 12 hours, and frequently do not include a lot, if any, navigation requirements. Many Sprint class races have marked courses, or the majority of the course will be marked, leaving only a small portion of the race course length to be navigated with map and compass skills.
• Medium or Endurance Length
  The majority of Endurance class races last from 12 to 36 hours and generally require some level of compass and map skills. The level of skills necessary to navigate successfully through these races varies from race to race, depending on the specific interests of the Race Directors.
• Long or Expedition Length
  Expedition class races are generally 2 days to 10 days in length and invariably require excellent navigation skills with a map and compass.