Active Duty None-Prior Service
- Army - 35 (must ship to basic training prior to 35th birthday. The Army experimented with raising the age limit to age 42 for a brief period of time, but effective April 1st, 2011, the Army has reverted to the lower age limit.
- Air Force - 27
- Navy - 34
- Marines - 28
- Coast Guard - Age 27. Note: up to age 32 for those selected to attend A-school directly upon enlistment (this is mostly for prior service).
Reserve Non-Prior Service
- Army Reserves - 35 (must ship to basic training prior to 35th birthday)
- Army National Guard - 35 (changed from 42 in 2009)
- Air Force Reserve - 34
- Air National Guard - 40 (Changed from 34 in Aug 2009)
- Naval Reserves - 39
- Marine Corps Reserve - 29
- Coast Guard Reserves - Age 39
Age waivers for non-prior service enlistments are very rare. The few I've seen approved involved those who started the enlistment process within the required age limits, but were unable to complete the process and ship to basic training before their birthday. In these cases, only a couple of months of age was waived.
Prior Service Enlistments
The age limit for prior service enlistment for most of the branches is the same as above, except that an individual's total previous military time can be subtracted from their current age. For example, let's say that an individual has four years of credible military service in the Marine Corps and wants to join the Air Force. The Air Force could waive the individual's maximum enlistment age to age 31 (Maximum age of 27 for the Air Force, plus four years credible service in the Marines).
For the Marine Corps and the Marine Corps Reserve, the maximum age of enlistment for prior service is 32, after computing the prior-service age adjustment.
For the Army and Air National National Guard, the maximum age for prior service enlistment is 59, as long as the member has enough years of prior service to be able to complete 20 years of creditable service for retirement by age 60.