How large is the federal debt?

Total federal debt—also known as gross debt—is the amount of the federal government's outstanding debt issued by the Treasury and other federal government agencies. Totaling about $13.6 trillion at the end of fiscal year 

Any yearly accounting period, regardless of its relationship to a calendar year. The fiscal year for the federal government begins on October 1 of each year and ends on September 30 of the following year; it is named by the calendar year in which it ends. Prior to fiscal year 1977, the federal government began its fiscal year on July 1 and ended it on June 30.2010, gross debt consists of two components: (1) debt held by the publicFederal debt held by all investors outside of the federal government, including individuals, corporations, state or local governments, the Federal Reserve and foreign governments. and (2) debt held by government accountsFederal debt owed to government accounts, primarily to federal trust funds such as Social Security and Medicare. The cumulative surpluses, including interest earnings, of these trust funds and other government accounts have been invested in Treasury securities, almost always nonmarketable. Whenever a government account needs to spend more than it takes in from the public, the Treasury must provide cash to redeem debt held by the government account. Consequently, this reflects a future burden on the economy. (also known as intragovernmental debt holdings), such as the Social Security and Medicare trust funds.http://www.gao.gov/special.pubs/longterm/debt/debtbasics.html#heldbypublic