The average age of accession is 54 years and 11 months. The youngest president elected to office was John F. Kennedy (age 43 years, 236 days). Theodore Roosevelt was sworn in after the assassination of William McKinley in 1901, making Kennedy the youngest president actually voted to the office, even though Roosevelt was president at age 42 years, 322 days.



Read more: The Top Ten: Youngest U.S. Presidents http://www.infoplease.com/toptens/youngpresidents.html#ixzz3bL4HoIRm