United States Population

With roughly 348 million people as of 2026, United States ranks 3rd in the world by population. In Other, where it lies, that future is driven by fertility, longevity and the movement of people across its borders. Population density stands at about 38 people for every square kilometre of land.

Growth continues for United States until around 2100, the year its population is set to crest at about 421 million. From there a slow fall takes it to roughly 421 million by century's end. The 200 million threshold was crossed near 1968.

Fertility sits at about 1.62 births per woman, below the replacement level of roughly 2.1, so without migration the population would eventually shrink. Net inward migration adds to the population each year and partly offsets the low birth rate.

Half of United States is currently younger than about 38, but by 2100 the median age is projected to reach around 45, even as life expectancy improves from about 79 years. That ageing slowly changes everything from the size of the workforce to the cost of care and pensions.

All of this is a projection, not a prediction. The further out it runs the wider the plausible range becomes, which is why United States's charts show a low-to-high band around the central line.