The Post-9/11 GI Bill can pay your full resident tuition at a public school.
If you are attending a private or foreign school it will pay up to $23,671.94 per academic year. An academic year lasts from Aug. 1 - Jul. 31 (changing to $24,476.79 Aug. 1, 2019).
Private schools can choose to participate in the "Yellow-Ribbon" program which can waive a portion of the difference in the tuition you are charged and the amount covered by the Post-9/11 GI Bill. Be sure to ask your school if they are planning to participate in the program.
The amount of tuition & fees covered by the GI Bill is determined by your Post-9/11-GI Bill entitlement percentage which is based on the number of months you have served on active duty after September 10, 2001. For example, if you have served 24 months active duty after September 10, 2001 your GI Bill percentage is 80%. If you are attending a public school as an in-state resident and the tuition is $10,000 a semester you would have 80% of your tuition and fees or $8,000 paid by the Post-9/11 GI Bill. Active duty time can also include Title 10 mobilizations for reservists & guard members.
Public schools must charge all eligible veterans who have been out of the military for less than 3 years, their dependents who are using transferred benefits, and the dependents using transferred benefits of active-duty members the resident tuition rate.