Marine Corps captains are commissioned officers who often hold company commander positions. Captain is the third officer rank, above both second and first lieutenants, and directly under major. The length of time it takes before a Marine is eligible for this rank depends on his level of education, how long he's been in service and his level of performance.

Educational Requirements

Commissioned officers in the Marines must have at least a bachelor's degree. If you enter the Marine Corps with a bachelor's degree, you've knocked off at least four years from your journey towards being a captain. If you enlist without an education, you can take advantage of the Special Education Program to earn a degree while receiving full-time pay and benefits. The SEP also pays some of the costs of your tuition and materials.

Commissioned Officer Requirements

On top of having a four-year degree, officer candidates must be U.S. citizens who are at least 20 but not yet 30 at the time of their commissioning. They must be able to pass rigorous fitness tests, demonstrate leadership potential and be able to pass thorough background checks. They must also pass a Scholastic Assessment Test, American College Test or Armed Services Vocational Aptitude Battery test prior to entering service.

Length of Service

Officers must have been in the Marine Corps for at least four years before they become eligible for promotion to captain. They also must spend at least two years serving as a first lieutenant, the rank directly below that of captain. Technically, someone could rise to this rank in as few as four years if he entered the service with a bachelor's degree. Promotions aren't based just on seniority, though. They must also be earned.

Other Promotional Considerations

The Marine Corps is only interested in promoting officers who have proven themselves to be dedicated, highly motivated and reliable individuals. Captain candidates' career records are reviewed thoroughly by a Selection Board made up of neutral senior officers. The Selection Board must also examine the current needs of the Marines, as the number of openings for captains is restricted by federal law. A slot must be available in order for a Marine to move up.