How many people are 18 or older in the US?

As of 2021, approximately 258 million people in the U.S. were 18 years old or older, which accounts for about 78% of the total population. This number is subject to change with new census data, but it provides a rough estimate of the adult population in the country. For the most current figures, checking the latest U.S. Census data or population estimates is recommended.