The U.S. population clock is based on a series of short-term projections for the resident population of the United States. This includes people whose usual residence is in the 50 states and the District of Columbia. These projections do not include members of the Armed Forces overseas, their dependents, or other U.S. citizens residing outside the United States.

The projections are based on a monthly series of population estimates starting with the April 1, 2010 resident population from the 2010 Census.

At the end of each year, a new series of population estimates, from the census date forward, is used to revise the postcensal estimates, including the population clock projections series. Once a series of monthly projections is completed, the daily population clock numbers are derived by interpolation. Within each calendar month, the daily numerical population change is assumed to be constant, subject to negligible differences caused by rounding.

Population estimates produced by the U.S. Census Bureau for the United States, states, counties, and cities or towns can be found on the Population Estimates web page. Future projections for the United States and states can be found on the Population Projections web page.

World Population

Source: U.S. Census Bureau, International Data Base

The Country Ranking tool provides a quick and easy method to view the most populous countries and areas of the world for any year between 1950 and 2050. The data for this tool are drawn from the International Data Base (IDB), which offers additional demographic information for each country.

“Top 10 Most Populous Countries,” projected to July 1, 2015.

To learn more about world population projections go to http://www.census.gov/population/popwnotes.html

United States data used in the IDB are based on official estimates and projections. All population estimates and projections are for the resident population. Population estimates for 2000-2012 are consistent with the 2010 Census. Population data in the IDB for 2013-2050 are based on the 2012 National Projections, Middle Series. Revised official population estimates are released each year (www.census.gov/popest), and projections are updated periodically (www.census.gov/population/projections). The official, current U.S. population estimates and projections may not match those shown in the IDB due to differences in the timing of their releases.

Coordinated Universal Time (UTC) is the equivalent of Eastern