The U.S. government is often referred to as the world’s biggest debtor. But how much debt does it owe? A visit to the website of the U.S. Department of the Treasury yields a bewildering array of different measures of U.S. federal government debt. Although the gross debt of the U.S. federal government is approaching $18 trillion, the debt that is subject to the debt limit is a few billion dollars smaller, while debt in the hands of the public is less than $13 trillion.