From the U.S. Census:
… the U.S. Census Bureau today projected the United States population will be 322,762,018 on Jan. 1, 2016.
This represents an increase of 2,472,745, or 0.77 percent, from New Year’s Day 2015. Since Census Day (April 1) 2010, the population has grown by 14,016,480, or 4.54 percent.
In 2016, the United States is expected to experience one birth every eight seconds and one death every ten seconds.
Meanwhile, net international migration is expected to add one person to the U.S. population every 29 seconds. The combination of births, deaths and net international migration increases the U.S. population by one person every 17 seconds.
The projected world population on Jan. 1 is 7,295,889,256, an increase of 77,918,825, or 1.08 percent, from New Year’s Day 2015. During January 2016, 4.3 births and 1.8 deaths are expected worldwide every second.