Millennials are still America's largest generation, with Gen Z close behind
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Millennials are still the largest generation in the United States, but Gen Z is close behind. In 2025 the country had about 73.1 million millennials and 72.2 million members of Gen Z, according to U.S. Census Bureau population estimates for July 1, 2025. Baby boomers, once the biggest group by far, are now third at about 66.6 million.
The Census Bureau does not define generations. These counts apply the birth years Pew Research Center uses to the bureau's estimates by single year of age: baby boomers born 1946 to 1964, Gen X 1965 to 1980, millennials 1981 to 1996, and Gen Z 1997 to 2012. Children born in 2013 or later are grouped here as Gen Alpha. Because the estimates are by age on July 1, each person's birth year is approximate, so the counts can be off by a few hundred thousand at each boundary.
| Rank | Generation | Born | Age in 2025 | Population | Share of U.S. |
|---|---|---|---|---|---|
| 1 | Millennials | 1981-1996 | 29-44 | 73,054,093 | 21.4% |
| 2 | Gen Z | 1997-2012 | 13-28 | 72,180,782 | 21.1% |
| 3 | Baby boomers | 1946-1964 | 61-79 | 66,559,500 | 19.5% |
| 4 | Gen X | 1965-1980 | 45-60 | 64,412,742 | 18.8% |
| 5 | Gen Alpha | 2013-2025 | 0-12 | 50,608,394 | 14.8% |
| 6 | Silent Generation and older | 1945 or earlier | 80 and older | 14,969,346 | 4.4% |
The two youngest adult generations are the only ones still growing much. Compared with the same birth years a year earlier, Gen Z added about 462,000 people and millennials about 276,000. No one new is being born into those years, so the gains come from net immigration.
The older generations are shrinking. The baby boom generation lost about 1.2 million people between 2024 and 2025, and the Silent Generation and older lost about 1.4 million. Gen X, now 45 to 60, was down about 250,000. Gen Alpha grew by 3.9 million, nearly all of it newborns, and has no agreed end year.
The total population in the estimate was 341,784,857. Millennials and Gen Z together make up 42.5 percent of it, and the four generations born from 1946 through 2012 make up 80.8 percent.
The boomers still shape the age of the country. The median age hit a record 39.4 in 2025, as our post on the record median age covers, and the 65-and-older population keeps growing as more boomers pass 65. The oldest boomers turned 79 in 2025, and the youngest turned 61.
The gap between millennials and Gen Z was about 873,000 people in 2025. A year earlier, comparing the same birth years, it was about 1.06 million.
Sources
U.S. Census Bureau, Vintage 2025 national population estimates by single year of age and sex, resident population, July 1, 2024, and July 1, 2025. Generation birth years follow Pew Research Center. Birth year is approximated as 2025 minus age on July 1, 2025, and year-to-year changes compare the same birth years in the 2024 and 2025 estimates.
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Which generation is the largest in the US?
Millennials, born 1981 to 1996, were the largest generation in 2025, with about 73.1 million people. Gen Z, born 1997 to 2012, was close behind at 72.2 million, based on Census Bureau estimates by age.
How many baby boomers are left in the US?
About 66.6 million baby boomers, born 1946 to 1964, lived in the United States on July 1, 2025, or 19.5 percent of the population. The generation lost about 1.2 million people between 2024 and 2025.
How many Gen X are there in the US?
About 64.4 million members of Gen X, born 1965 to 1980, lived in the United States in 2025, 18.8 percent of the population. They were 45 to 60 years old, and the group shrank by about 250,000 in a year.
